In this action for breach of contract and violation of trade secrets, the IAS court erroneously charged the jury in a way that left a clear impression that the burden of proof was on the plaintiff that he, and not a successor corporation, was the real party in interest. The defendant bears the burden of proof on an affirmative defense (see, e.g., Kramer v City of New York, 173 A.D.2d 155, lv denied 78 N.Y.2d 857), including one that asserts that the plaintiff is not the real party in interest (Cleary v Dykeman, 162 App. Div. 897). The erroneous charge on the burden of proof warrants a new trial (see, Wilson v Nationwide Mut. Ins. Co., 168 A.D.2d 912, lv dismissed 77 N.Y.2d 940).
In view of the foregoing we need not reach plaintiff's other arguments.
Concur — Carro, J.P., Rosenberger, Ellerin, Kupferman and Ross, JJ.