How can you find out if a phrase is a registered trademark?

Trademarks are registered with the USPTO. You can check registered trademarks to see whether your phrase has already been taken (a href="http://tess2.uspto.gov/bin/gate.exe?f=searchss&state=4007:gkkfme.1.1)." rel="nofollow"http://tess2.uspto.gov/bin/gate.exe?f=se…/a That being said, you probably wont know for sure if you can use it as a trademark until you file an application with the PTO.