We describe a 45-yr-old man, who presented with primary infertility of 2 yr. He had small testicles with severe oligoasthenozoospermia and low serum gonadotropins, but normal serum T. The suppression of gonadotropin secretion by increased adrenal steroids due to untreated 21-hydroxylase deficiency appeared to underlie the failure in spermatogenesis. Hydrocortisone treatment was started and was modified later to include prednisolone to get optimal suppression of the secretion of ACTH and adrenal steroids. Within a few months, the gonadotropin levels became normal, and spermatogenesis was improved. A normal pregnancy was achieved.