In a collaborative study, 48 prepubertal boys with undescended testes ranging in age from 15 months to 11 years were treated with low-dose intranasal buserelin following an every-other-day programme for a period of 6 months. Urinary LH, FSH, and testosterone were not altered during the treatment period. Boys over 7 years of age experienced a slight but significant rise in testosterone at the end of treatment. Testicular descent was achieved in only 17% of boys. In the remainder, bilateral testicular biopsies were obtained during orchiopexy. Grouped analysis showed a significant increase in the number of germ cells per tubule in both unilateral and bilateral cryptorchid boys, suggesting that buserelin treatment of the testis in a cryptorchid position is capable of improving fertility potential. If time-matched controls are compared to treated boys of the same age, again a significant difference is observed indicating that buserelin treatment does increase the germ cell count.