Whether commencing a lawsuit or planning for the defence of one, the potential for counterclaims is an important strategic consideration. US civil procedure rules permit, and sometimes require, that parties pursue counterclaims in response to being sued. Antitrust counterclaims can be pursued in a variety of types of cases, but are most prevalent in intellectual property litigation. The assertion of antitrust counterclaims can increase the cost of litigation, add risk for the party bringing the lawsuit, and alter the relative positions of the parties to the case. Given the possible impact on litigation, potential counterclaims should be given careful consideration.