Appellant challenges his conviction for violating 21 U.S.C. § 174 on the ground *532 that the evidence was insufficient to sustain the district court’s implied finding of possession of heroin and that the failure to prove possession destroyed the foundation for invoking the statutory inference of knowledge of illegal importation.

There was evidence that appellant had actual possession of part of the heroin and constructive possession of the remainder. Appellant’s acquittal upon the sale counts is not inconsistent with his conviction for receiving and concealing the heroin. The district court believed that part of the testimony relating to appellant’s possession, and it discredited the testimony connecting appellant to the sales. Questions of credibility lie within the exclusive province of the district court.

The judgment is affirmed.