Testicular descent has been reported to be a dihydrotestosterone (DHT) dependent event. To further elucidate the role of DHT in the process of testicular descent, a group of rats were treated with the 5-alpha reductase inhibitor, 4-MAPC, from birth to day 28 of age and the incidence of testicular descent as well as ventral prostate weight was noted at day 29 of age. It was determined that in the doses used, 4-MAPC failed to prevent testicular descent. Because 4-MAPC inhibited ventral prostate weight by only 53% (as compared to a 75% inhibition by castration), the failure of the 4-MAPC to prevent testicular descent could be due to its inability to completely inhibit tissue 5-alpha reductase activity. The results of this study do not mitigate against the role of other nonhormonal factors working in tandem with DHT in the induction of testicular descent in this animal model.