Standard gonadotropin stimulation tests of ovarian function and basal plasma prolactin measurements have been carried out in 151 patients with amenorrhea or severe oligomenorrhea. In 90 of these a standardized multiple pituitary stimulation test, including the prolactin response to thyrotropin releasing hormone, was also performed. There was a tendency for the basal estrogen excretion and the ovarian response to gonadotropin to be lower in patients with hyperprolactinemia. These correlations were weak and did not reach the levels of statistical significance except when compareing the ovariance response in patients with mild hyperprolactinemia to those with moderate or severe hyperprolactinemia. It is concluded that, in women, elevated plasma prolactin levels have little, if any, direct inhibitory influence on the ovariance response to gonadotropins in vivo.