Appellant was convicted and sentenced for interstate transportation of a stolen motor vehicle in violation of 18 U.S.C. § 2312 (1964), the Dyer Act. He appeals on the ground that the proofs before the District Judge were insufficient to establish that'he had knowledge that the stolen car in which he was arrested was stolen.

Our review of the evidential record indicates that there was ample evidence from which the District Judge could properly have inferred that he did have such knowledge.

Among other evidential factors, appellant’s testimony was in direct conflict with that of the owner of the stolen automobile. The District Judge believed the latter. The credibility of wit *221 nesses is an issue for the trier of the facts. Butzman v. United States, 205 F.2d 343 (6th Cir.), cert. denied, 346 U.S. 828, 74 S.Ct. 50, 98 L.Ed. 353 (1953).

Affirmed.