Tekelec

Filed Pursuant to Rule 424(b)(3)
Registration No. 333-108821

PROSPECTUS SUPPLEMENT NO. 1 DATED MAY 21, 2004

$125,000,000

(TEKELEC LOGO)

2.25% Senior Subordinated Convertible Notes Due 2008 and
Common Stock Issuable Upon Conversion Thereof

The purpose of this supplement is to amend and supplement the prospectus dated December 12, 2003 relating to the offer for resale of up to $125,000,000 aggregate principal amount of Tekelec’s 2.25% Senior Subordinated Convertible Notes due 2008 and such shares of Tekelec common stock as may be issued upon conversion of the notes.

The prospectus is hereby amended and supplemented to include in the “Selling Securityholders” table the information in the table set forth below regarding an increase in the principal amount of the notes held by two of the selling securityholders. The table is based upon information provided to us by or on behalf of the selling securityholders and indicates as of the date of this prospectus supplement:

• the maximum aggregate principal amount of the notes that the selling securityholder may offer under the prospectus;

• the number of shares of Tekelec common stock beneficially owned by the selling securityholder that may be offered by the selling securityholder under the prospectus; and

• the number of shares of common stock that the selling securityholder will beneficially own upon completion of the offering under the prospectus.

Principal

Number of

Amount of

Shares of

Number of

Shares of

Notes

Common Stock

Shares of

Common Stock

Beneficially

Percentage

Beneficially

Common Stock

Beneficially

Owned That

of Notes

Owned Prior to

That May

Owned After

Name

May Be Sold

Outstanding

the Offering⁽¹⁾

Be Sold⁽²⁾

the Offering

Man Convertible Bond Master Fund, Ltd.

8,095,000

6.5

411,959

St. Thomas Trading, Ltd.

12,105,000

9.7

616,030

¹		Does not include shares of common stock issuable upon conversion of the notes.

²		Represents shares of common stock issuable upon conversion of the notes and assumes conversion at the initial rate of 50.8906 shares of common stock per $1,000 principal amount of notes. This conversion rate and the number of shares issuable upon conversion are subject to adjustment under certain circumstances.

The date of this prospectus supplement is May 21, 2004.