• A study was conducted in boys with bilateral cryptorchidism, who were to undergo surgical orchiopexy, to determine if target-organ androgen insensitivity might play a role in the failure of the testes to descend into the scrotum. Nine boys older than 1 year in whom bilateral undescended testes was the only genitourinary abnormality were evaluated. Each subject was administered a six-week course of human chorionic gonadotropin (hCG), 3000 U/m2 of body surface area, intramuscularly injected daily for five days and then twice per week. Basal and hCG-stimulated levels of testosterone were normal. However, hCG administration failed to induce testicular descent in all cases. At the time of surgery, scrotal skin and testicular biopsy specimens were obtained for propagation of cells in tissue culture. Androgen receptor levels and binding affinity were normal for the androgen-specific ligands dihydrotestosterone and metribolone in both skin fibroblasts and testicular cells. In addition, 5α-reductase activity was normal in scrotal skin fibroblasts. Nine boys with bilateral cryptorchidism and normal testicular androgen biosynthesis had normal androgen receptor-binding activity and 5α-reductase activity in cultured scrotal skin fibroblasts and testicular cells. Therefore, bilateral maldescent of the testes in these boys with cryptorchidism was not due to androgen insensitivity.