Microsoft is suing Motorola for infringing on its smart-phone patents.
The software maker on Friday said Motorola phones that use Google's Android software step on Microsoft technology. The functions in question include synchronizing e-mail, calendars and contacts.
Microsoft filed its lawsuit in the U.S. District Court for the Western District of Washington. It also filed a claim with the International Trade Commission.
Microsoft said Motorola licensed some of its mobile technology from 2003 to 2007, but did not renew the license even as the handset maker continued to use the technology.
This isn't the first move Microsoft has made to protect its mobile patents. In April, it announced licensing agreement with another Android phone maker, Taiwan's HTC .
A spokeswoman for Schaumburg, Ill.-based Motorola said the company has not seen the lawsuit and therefore can't comment on its contents.
"Motorola has a leading intellectual property portfolio, one of the strongest in the industry, and we will vigorously defend ourself in this matter," spokeswoman Jennifer Erickson said.
Erickson declined to comment on Microsoft's assertion that the company licensed the technology in the past, but has since let the license lapse.