Medical treatment with FSH and HCG was tested during 21 days in 47 cases (76 testis) of undescended testis. The average testis size, as measured by ecography, increased from 0.828 cc to 1.57 cc 48 hours after completing the treatment. Three months later the average testis size was 1.025 cc and 1.24 cc at six months. FSH increased slightly and total testosterone and free testosterone increased significantly. After treatment, 68% of the previously undescended testis descended.