OPINION

Appellant was convicted by a jury of the sale of a controlled substance (heroin), in violation of NRS 453.161 and 453.321, and subsequently sentenced to a term of fifteen years in Nevada State Prison, with credit for time served. His only contention on this appeal is that the evidence adduced at trial was insufficient to support his conviction.

This contention is without merit. Two undercover police officers testified that appellant offered to sell them some *536“junk”, which they understood to mean heroin. Each further testified that after negotiating a price, appellant left, then returned with a red balloon. Upon ascertaining that the material inside appeared to be heroin, the officers gave appellant money in exchange for the balloon. They then placed appellant under arrest. An expert witness identifed the substance in the balloon as heroin.

While appellant and his companion gave a different version of these events at trial, the credibility of witnesses and the weight of the evidence is solely within the province of the jury. So long as the verdict is supported by substantial evidence in the record, it will not be disturbed on appeal. Azbill v. State, 88 Nev. 240, 495 P.2d 1064 (1972); Sanders v. State, 90 Nev. 433, 529 P.2d 206 (1974); Wheeler v. State, 91 Nev. 119, 531 P.2d 1358 (1975); Wise v. State, 92 Nev. 181, 547 P.2d 314 (1976).