The effect of treatment of 73 boys (mean age 7 years) with undescended testes with human chorionic gonadotropin (hCG) was related to the testicular status at birth as recorded in their birth charts. In 24 boys with diagnosed congenital cryptorchidism, hCG treatment was unsuccessful in 19 cases and operation was performed. In the remaining 5 boys hCG treatment alone was sufficient. Forty-nine boys had normal scrotal testes at birth and hCG therapy was successful in 38, while the remaining 11 required surgical correction. It is concluded that knowledge of the testicular status at birth is of value in clinical practice to evaluate the prognosis of treatment with hCG.