Six patients with all of the clinical and laboratory characteristics of isolated hypogonadotropic hypogonadism (bihormonal gonadotropin deficiency) were treated with human menopausal gonadotropins (hMG, Pergonal) and human chorionic gonadotropin (hCG). Of a total of 37 courses of treatment administered, there was evidence of ovulation in 32 (29%). The first four subjects had a total of six pregnancies in 13 treatment cycles. In the remaining two subjects, there were abnormalities in the seminal fluid of both husbands and, as a consequence, only one patient conceived. The average dose and duration of hMG therapy was 3310 IU (44 ampules), administered for 13 days. A wide range of hCG dosage was used to induce ovulation, but three subjects conceived following 5000 IU of hCG on 2 successive days. None of our subjects developed any evidence of the hyperstimulation syndrome, and there was only one instance of twin birth. Serial determinations of hLH performed during hMG therapy were lower than those noted during the normal follicular phase. In contrast, hFSH levels were in the normal follicular phase range. the high success rate in these subjects indicates that the prognosis for inducing ovulation in patients with hypogonadotropic hypogonadism is good.