Press Release

Cingular Wireless Joins Palm Powered Mobile World

Company to collaborate with PalmSource to accelerate availability of Palm OS software solutions for Palm Powered smartphones

San Jose, California, PalmSource Mobile Summit and Developer Conference, May 24, 2005 — PalmSource, Inc. (NASDAQ: PSRC), provider of Palm OS®, a leading operating system powering next generation phones and mobile devices today announced Cingular Wireless has joined the Palm Powered™ Mobile World (PPMW) program. The combination of PalmSource and Cingular Wireless is expected to speed availability of third–party Palm OS software solutions designed for Palm Powered mobile devices.

Following the recent merger with AT&T Wireless, an existing PPMW mobile operator partner, Cingular Wireless joins Orange, Sprint and Telefónica Móviles España in addition to more than a dozen infrastructure and middleware partners in the PPMW program to capitalize on the growing mobile phone market. Leveraging the collaboration efforts of PalmSource and AT&T Wireless, Cingular Wireless will work together with PalmSource in a number of areas including:

• Collaborating with the 400,000–plus registered Palm OS developer community for the development of third–party Palm OS applications tailored to the needs of the newly combined Cingular Wireless;
• Engaging in joint marketing activities to identify and promote key third–party Palm OS applications and solutions to business customers; and
• Collaborating to align the Palm OS platform roadmap with the product requirements of Cingular Wireless in order to facilitate the deployment of next generation of Palm Powered devices

Cingular Wireless is the largest wireless company in the United States with more than 50 million wireless subscribers worldwide. The Company currently offers its wireless customers a wide range of mobile phone offerings including the Palm Powered Treo 650 from palmOne.

"Joining the Palm Powered Mobile™ World program reinforces our commitment to providing our customers with the broadest selection of wireless solutions for Palm Powered mobile devices," said Abhi Ingle, executive director for Cingular's Business Markets Group. "We look forward to our continued collaboration with PalmSource to offer our wireless customers more cutting–edge Palm Powered devices, like the Treo 650, that deliver a superior user experience."

"PalmSource is committed to collaborating with industry–leading mobile operators to further accelerate the growth of the Palm Powered™ economy," said Albert Chu, vice president of business development and wireless, PalmSource, Inc. "We believe the combination of Palm OS® and Cingular's wireless data network provides Palm OS handsets vendors and software developers a truly robust environment to develop leading–edge mobile devices and software solutions."

About Palm Powered Mobile World
The Palm Powered Mobile World program connects mobile operators, infrastructure and middleware partners and software developers in a wireless Palm Powered economy designed to bring Palm OS software applications and solutions to market, provide increased revenue opportunities for partners and a superior experience for users of Palm Powered mobile devices. More information on the Palm Powered Mobile World program can be found at: www.palmsource.com/partners.

About PalmSource
PalmSource, Inc., the company behind Palm OS®, a leading operating system powering smart mobile devices, is a leading developer of software for mobile phones and other mobile devices. Its products include a wide range of software for mobile phones at all price points. More than 39 million mobile phones, handhelds, and other mobile devices run PalmSource software. More than 45 companies worldwide have licenses to PalmSource software, including Fossil, Garmin, GSPDA, Kyocera, Lenovo, palmOne, Samsung, Sony, and Symbol Technologies. Palm OS has given rise to a large community of users, enterprises, developers and manufacturers, who together make up the Palm Powered Economy. More information about PalmSource is available at www.palmsource.com, www.palmsource.co.uk, www.palmsource.fr, www.palmsource.de, www.palmsource.com/es and www.palmsource.com.cn.

CAUTIONARY NOTE REGARDING FORWARD–LOOKING STATEMENTS: This press release contains forward–looking statements that involve risks and uncertainties, as well as assumptions that if they never materialize or prove incorrect, could cause our results to differ materially from those expressed or implied by such forward–looking statements. Such forward–looking statements include, without limitation, statements regarding our collaboration with Cingular and the Palm Powered Mobile World program. The risks and uncertainties that could cause our results to differ materially from those expressed or implied by such forward–looking statements include, without limitation, our ability to collaborate successfully with Cingular and other Palm Powered Mobile World partners; the ability of Cingular to successfully optimize its offering for Palm OS and to build a product portfolio that includes comprehensive support for Palm Powered devices; our ability to successfully leverage mobile operator networks using Cingular's services; our ability to enter into new relationships with leading mobile operators, infrastructure partners and software developers to create innovation and differentiation in the global phone an mobile device markets; realization of the anticipated benefits of the Palm Powered Mobile World program; and other risks and uncertainties contained in our public announcements, reports to stockholders and other documents filed with and furnished to the Securities and Exchange Commission, including our Annual Report on Form 10–K for the period ended May 28, 2004 and our Quarterly Report on Form 10–Q for the periods ended August 27, 2004, November 26, 2004 and February 25, 2005. All forward–looking statements in this press release are based on information available to us as of the date hereof, and we assume no obligation to update these forward–looking statements.

Copyright © 2005, PalmSource, Inc. PalmSource and Palm OS are trademarks or registered trademarks of PalmSource, Inc. or its affiliate in the United States, France, Germany, Japan, the United Kingdom, and other countries. These marks may not be used in connection with any product or service that does not belong to PalmSource, Inc. (except as expressly permitted by a license with PalmSource, Inc.), in any manner that is likely to cause confusion among customers, or in any manner that disparages or discredits PalmSource, Inc., its licensor, its subsidiaries or affiliates. All other brands, product names, company names, trademarks and service marks are the properties of their respective owners. All rights reserved.