Unstable patterns of serum LH, FSH, and T concentration were demonstrated during frequent interval sampling in 4 normal men. No consistent relationship of T levels to the onset of LH rises could be seen. However, onethird of the LH peaks was followed by a rise in T levels and each T elevation was preceded by an LH peak. The frequency of release and half-times of disappearance for LH and FSH did not change during clomiphene treatment in 2 of these normal subjects (100 mg/day); elevated serum gonadotropins resulted from an increased magnitude of release per pulse. A similar exaggeration of T secretion was seen. Testosterone propionate injection (25 mg) on day 4 of clomiphene treatment further elevated circulating T levels without lowering serum gonadotropins.