Apple is suing Motorola for infringing on patents related to its smart phones.
Apple Inc. said in a filing on Friday that Motorola's Droid, Cliq, BackFlip and other phones violate its patents related to the iPhone's touch screen and user interface.
Apple says it wants Motorola Inc. to stop using the patents and is seeking an unspecified amount of damages as well as its attorneys' fees and costs.
The lawsuit was filed in a federal district court in Wisconsin on Friday.
The suit comes after Motorola sued Apple earlier this month over patent infringement.
Motorola was the second-largest phone maker in 2006, due to the popularity of its Razr clamshell phone, but it was surpassed by others when smart phones became popular.
Meanwhile, Apple Inc.'s iPhones have surged in popularity. The company sold 14.1 million on them in June through September.
Now, Motorola is the seventh-largest phone maker in the world. In North America it's outstripped by Apple Inc. and Research In Motion Ltd., the maker of the BlackBerry. Motorola's recent smartphones such as the "Droid" line of phones run on Google Inc.'s Android software.