UNITED STATES

                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549


                                  SCHEDULE 13G
                  UNDER THE SECURITIES AND EXCHANGE ACT OF 1934

                             Allion Healthcare, Inc.
-------------------------------------------------------------------------------
                                (Name of Issuer)

                          Common Stock, $.001 par value
-------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    141653105
-------------------------------------------------------------------------------
                                 (CUSIP NUMBER)

                                  April 4, 2003
-------------------------------------------------------------------------------
             (Date of Event Which Requires Filing of This Statement)

Check the  appropriate box to designate the rule pursuant to which this Schedule
is filed:
[  ]  Rule 13d-1(b)
[X]   Rule 13d-1(c)
[  ]  Rule 13d-1(d)





CUSIP No. 141653105

1. Names of  Reporting  Persons,  I.R.S.  Identification  Nos. of above  persons
(entities only).

Principal Financial Group, Inc.
-------------------------------------------------------------------------------

2. Check the Appropriate Box if a Member of a Group (See Instructions)

(a) [X]

(b) [  ]

3. SEC Use Only

-------------------------------------------------------------------------------

4.  Citizenship or Place of Organization

                             Delaware
-------------------------------------------------------------------------------

                                      5.  Sole Voting Power

                                      -----------------------------------------

NUMBER OF                             6.  Shared Voting Power
SHARES
BENEFICIALLY                                        733,334
OWNED BY                              -----------------------------------------
EACH
REPORTING                             7.  Sole Dispositive Power
PERSON WITH
                                      -----------------------------------------

                                      8.  Shared Dispositive Power

                                                    733,334
                                      -----------------------------------------

9. Aggregate Amount Beneficially Owned by Each Reporting Person

                             733,334
-------------------------------------------------------------------------------

10. Check Box if the Aggregate Amount in Row (11) Excludes Certain Shares

                                                                        [  ]

11. Percent of Class Represented by Amount in Row (11)

                             19.13%
-------------------------------------------------------------------------------


                                       2


12.  Type of Reporting Person

                             HC
-------------------------------------------------------------------------------


1. Names of  Reporting  Persons,  I.R.S.  Identification  Nos. of above  persons
(entities only).

Principal Financial Services, Inc.
-------------------------------------------------------------------------------


2. Check the Appropriate Box if a Member of a Group (See Instructions)

(a) [X]

(b) [  ]

3. SEC Use Only

-------------------------------------------------------------------------------

4.  Citizenship or Place of Organization

                             Iowa
-------------------------------------------------------------------------------


                                      5.  Sole Voting Power

                                                    0
                                      -----------------------------------------

NUMBER OF                             6.  Shared Voting Power
SHARES
BENEFICIALLY                                        733,334
OWNED BY                              -----------------------------------------
EACH
REPORTING                             7.  Sole Dispositive Power
PERSON WITH
                                                    0
                                      -----------------------------------------

                                      8.  Shared Dispositive Power

                                                    733,334
                                      -----------------------------------------


9. Aggregate Amount Beneficially Owned by Each Reporting Person

                             733,334
-------------------------------------------------------------------------------

10. Check Box if the Aggregate Amount in Row (11) Excludes Certain Shares

                                                                   [  ]


                                       3


11. Percent of Class Represented by Amount in Row (11)

                             19.13%
-------------------------------------------------------------------------------

12.  Type of Reporting Person

                             HC
-------------------------------------------------------------------------------



1. Names of  Reporting  Persons,  I.R.S.  Identification  Nos. of above  persons
(entities only).

Principal Life Insurance Company
-------------------------------------------------------------------------------

2. Check the Appropriate Box if a Member of a Group (See Instructions)

(a) [X]

(b) [  ]

3. SEC Use Only

-------------------------------------------------------------------------------

4.  Citizenship or Place of Organization

                             Iowa
-------------------------------------------------------------------------------


                                      5.  Sole Voting Power

                                                    0
                                      -----------------------------------------

NUMBER OF                             6.  Shared Voting Power
SHARES
BENEFICIALLY                                        733,334
OWNED BY                              -----------------------------------------
EACH
REPORTING                             7.  Sole Dispositive Power
PERSON WITH
                                                    0
                                      -----------------------------------------

                                      8.  Shared Dispositive Power

                                                    733,334
                                      -----------------------------------------


9. Aggregate Amount Beneficially Owned by Each Reporting Person

                             733,334
-------------------------------------------------------------------------------


                                       4


10. Check Box if the Aggregate Amount in Row (11) Excludes Certain Shares

                                                                      [  ]

11. Percent of Class Represented by Amount in Row (11)

                             19.13%
-------------------------------------------------------------------------------

12.  Type of Reporting Person

                             IC
-------------------------------------------------------------------------------

ITEM 1.  ISSUER.

The issuer is Allion Healthcare, Inc., whose principal offices are located at 33
Walt Whitman Road, Suite 200A Huntington Station, NY 11746.

ITEM 2.  IDENTITY AND BACKGROUND.

This  statement  relates  to  shares of Series B  Preferred  Stock and  Series C
Preferred Stock, in each case convertible into shares of Common Stock, $.001 par
value of Allion Healthcare,  Inc., CUSIP No. 141653105.  This statement is being
filed by: (i) Principal Financial Group, Inc. ("PFG"),  (ii) Principal Financial
Services, Inc. ("PFS") and Principal Life Insurance Company ("PLIC").

PFG is a corporation  incorporated under the laws of the State of Delaware.  Its
common stock is publicly  traded on the New York Stock Exchange under the ticker
symbol PFG. PFG is a holding company.  The address of its principal business and
principal office is 711 High Street, Des Moines, Iowa 50392.

PFS, an Iowa  corporation,  is a  wholly-owned  subsidiary  of PFG and a holding
company.  Its  principal  business and  principal  office is located at 711 High
Street, Des Moines, Iowa 50392.

PLIC is a stock insurance company organized under the laws of the State of Iowa.
The  principal  business  activity  of PLIC is the  provision  of  products  and
services for businesses,  groups and individuals including individual insurance,
pension plans and group/employee benefits. The address of its principal business
and principal office is 711 High Street, Des Moines, Iowa 50392.

By virtue of their  ownership and control of PLIC, PFG and PFS have the ultimate
voting  and  dispositive  power with  respect to the shares of Allion  Preferred
Stock  held by PLIC and may be  deemed  indirect  beneficial  owners  of all the
shares of Allion  Preferred  Stock  owned by PLIC  within  the  meaning  of Rule
13d-3(a) under the Securities Exchange Act of 1934, as amended (the "Act").

ITEM 3.  NOT APPLICABLE.


                                       5


ITEM 4.  OWNERSHIP.

Provide the following  information regarding the aggregate number and percentage
of the class of securities of the issuer identified in Item 1.

     (a)  Amount beneficially owned:      733,334
                                      --------------.

     (b)  Percent  of  class:      19.13
                              ----------------.

     (c)  Number of shares as to which the person has:

         (i) Sole power to vote or to direct the vote __________.

         (ii) Shared power to vote or to direct the vote    733,334
                                                       --------------.

         (iii) Sole power to dispose or to direct the disposition of_____.

         (iv) Shared power to dispose or to direct the  disposition of 733,334
                                                                      --------.

ITEM 5.  NOT APPLICABLE.

ITEM 6.  NOT APPLICABLE.

ITEM 7.  IDENTIFICATION  AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED
         THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY OR CONTROL
         PERSON.

                               See Item 2.

ITEM 8.  SEE EXHIBIT A.

ITEM 9.  NOT APPLICABLE.

ITEM 10.  CERTIFICATION.

              By signing  below I certify  that, to the best of my knowledge and
              belief, the securities referred to above were not acquired and are
              not held for the  purpose  of or with the  effect of  changing  or
              influencing  the control of the issuer of the  securities and were
              not  acquired  and  are  not  held  in  connection  with  or  as a
              participant in any transaction having that purpose or effect.




                                       6




                                   SIGNATURES

After reasonable inquiry and to the best of the Reporting Person's knowledge and
belief,  the Reporting  Person  certifies that the information set forth in this
statement is true, complete and correct.

April 14, 2003
-------------------------------------------------------------------------------
Date

PRINCIPAL FINANCIAL GROUP, INC.

By:   /S/ JOYCE N. HOFFMAN
      -----------------------
        Joyce N. Hoffman
        Senior Vice President & Corporate Secretary



PRINCIPAL FINANCIAL SERVICES, INC.

By:   /S/ JOYCE N. HOFFMAN
      -----------------------
        Joyce N. Hoffman
        Senior Vice President & Corporate Secretary



PRINCIPAL LIFE INSURANCE COMPANY

By:   /S/ JOYCE N. HOFFMAN
      -----------------------
        Joyce N. Hoffman
        Senior Vice President & Corporate Secretary




                                       7



                                    EXHIBIT A

                             JOINT FILING AGREEMENT



         In accordance  with Rule 13d-1(k) under the Securities  Exchange Act of
1934, as amended,  each of the parties hereto agrees with the other parties that
the  statement  of  Schedule  13G  pertaining  to certain  securities  of Allion
Healthcare, Inc. to which this agreement is an exhibit is filed by and on behalf
of each such  party and that any  amendment  thereto  will be filed on behalf of
each such party.

Dated:   April 14, 2003

                                        PRINCIPAL FINANCIAL GROUP, INC.


                                        By:     /S/ JOYCE N. HOFFMAN
                                           -------------------------------
                                            Joyce N. Hoffman
                                            Senior Vice President & Corporate
                                              Secretary



                                        PRINCIPAL FINANCIAL SERVICES,
                                          INC.


                                        By:     /S/ JOYCE N. HOFFMAN
                                           -------------------------------
                                            Joyce N. Hoffman
                                            Senior Vice President & Corporate
                                              Secretary



                                        PRINCIPAL LIFE INSURANCE
                                          COMPANY


                                        By:     /S/ JOYCE N. HOFFMAN
                                           -------------------------------
                                            Joyce N. Hoffman
                                            Senior Vice President & Corporate
                                              Secretary