Apple is taking Samsung to court over its design of the Galaxy phone and tablet range which the company thinks is too similar to the iPhone and iPad.
Apple's claim is centred on the design features of the Galaxy, such as the style of its screen symbols. Samsung said it would contest the allegations because it conducted its own development and research.
Galaxy products use Google's Android operating system, which directly competes against Apple's iPhone software. As well as being in competition, Samsung supplies microchips for Apple, such as the A4 and A5 processors, as well as MacBook Pro memory chips.
The lawsuit, which was filed on Friday 15 April 2011, alleges Samsung infringed Apple's trademarks and patents. Apple said in a statement: "This kind of blatant copying is wrong."
Impatient over patent
Samsung responded by saying: "Development of core technologies and strengthening our intellectual property portfolio are keys to our continued success." The Korean technology giant also said that it will contest the allegations "through appropriate legal measures to protect our intellectual property".
CCS Insight analyst, John Jackson, said Samsung is essentially Apple's only real tablet competitor at this stage.
Apple is just one name in a whole series of lawsuits between phone makers and software companies over who owns smartphone patents. Recently, Nokia sued Apple, which in turn sued handset maker HTC Corp.
Apple is bringing 16 claims against Samsung, including trademark infringement, unjust enrichment and 10 patent claims.