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                UNITED STATES SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                           FORM 10-K/A AMENDMENT NO. 1

    Annual report pursuant to Section 13 or 15(d) of the Securities Exchange
            Act of 1934 for the fiscal year ended December 31, 1998.

                         Commission file number: 0-23296

                               CIDCO INCORPORATED
             (Exact Name of Registrant as Specified in its Charter)

                  Delaware                             13-3500734
       (State or other jurisdiction of                (IRS employer
       Incorporation or organization)             identification number)

                               220 Cochrane Circle
                              Morgan Hill, CA 95037
              (Address of principal executive offices and zip code)

                                 (408) 779-1162
              (Registrant's telephone number, including area code)
              ----------------------------------------------------

        Securities registered pursuant to Section 12(b) of the Act: None

          Securities registered pursuant to Section 12(g) of the Act:
                          Common Stock, par value $.01

Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the  preceding 12 months (or for such  shorter  period that the  Registrant  was
required  to file  such  reports),  and  (2) has  been  subject  to such  filing
requirements for the past 90 days.

                                    YES X    NO
                                       ---     ---

Indicate by check mark if disclosure of delinquent  filers  pursuant to Item 405
of Regulation  S-K is not contained  herein,  and will not be contained,  to the
best  of  the  Registrant's   knowledge,  in  definitive  proxy  or  information
statements  incorporated  by  reference  in Part  III of this  Form  10-K or any
amendment to this Form 10-K. ( X )

The  aggregate  market value of the voting stock held by  non-affiliates  of the
Registrant  based on the closing  sale price of such stock at $4.00 on March 25,
1999 was $37,339,240.  Shares of Common Stock held by each executive officer and
director and by each person who owns 5% or more of the outstanding  Common Stock
have been  excluded in that such  persons may be deemed to be  affiliates.  This
determination of affiliate status is not necessarily a conclusive  determination
for other purposes.

Number of shares outstanding of the Registrant's Common Stock on March 25, 1999:
13,383,010

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                               CIDCO INCORPORATED

Item   8.     Financial Statements and Supplementary Data

The following Balance Sheet replaces the original in its entirety:

                                  BALANCE SHEET
                      (in thousands, except per share data)

                                                             December 31,
                                                      -------------------------
                                                           1998            1997
                                                      ---------       ---------
ASSETS
Current assets:
Cash and cash equivalents .........................   $  12,349       $  48,253
Short-term investments ............................      13,975          26,486
Accounts receivable, net of allowances for
    doubtful accounts of $1,885 and $3,301 ........      27,689          58,082
Inventories .......................................      22,086          12,904
Deferred tax asset ................................       1,490          11,808
Income tax refund receivable ......................      18,367              --
Other current assets ..............................       1,547           1,306
                                                      ---------       ---------
   Total current assets ...........................      97,503         158,839
Property and equipment, net .......................       9,691          12,591
Other assets ......................................         473           1,998
                                                      ---------       ---------
                                                      $ 107,667       $ 173,428
                                                      =========       =========

LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
Accounts payable ..................................   $  12,446       $  29,868
Accrued liabilities ...............................      14,585          10,955
Accrued taxes payable .............................         234           1,875
                                                      ---------       ---------
   Total current liabilities ......................      27,265          42,698

Commitments and contingencies (Notes 7 and 8)
Stockholders' equity:
Common stock, $.01 par value; 35,000 shares
    authorized, 14,418 and 14,418 shares issued ...         144             144
Treasury Stock, at cost (339 and 463 shares) ......      (4,600)         (6,163)
Additional paid-in capital ........................      88,916          88,763
Retained earnings (deficit) .......................      (4,058)         47,986
                                                      ---------       ---------
   Total stockholders' equity .....................      80,402         130,730
                                                      ---------       ---------
                                                      $ 107,667       $ 173,428
                                                      =========       =========

The notes  presented in the original  10-K are an integral part of the financial
statements.