Urinary hebin (strength 1 ec.=20 cc. pregnancy urine) was injected into two series of 20-day-old [male] rats daily for 30 days. Group 1 received 1/5 cc; group 2 received 1/2 cc. Representatives of each group were examined at intervals during this period. As compared with controls, the injected rats showed no hastening of spermatogenesis, more interstitial tissue, increased weight of testes, and enlarged seminal vesicles.