Sulpiride and TRH were used to evaluate the dynamics of prolactin (Prl) release in normoprolactinaemic, amenorrhoeic and normally menstruating women. The two tests were performed in a randomomized order with an interval of 2-3 days. In the normal women the first test was carried out between days 2 and 4 of their cycle. Basal values during the two tests were not statistically different (9.6 +/- 1.2 SE vs. 10.7 +/- 1.4 ng/ml in amenorrhoeic women with sulpiride and 11.3 +/- 1.4 vs. 12.4 +/- 1.7 in amenorrhoeic women during the TRH test). The two tests were performed while the subjects of the two groups had identical serum oestrogen concentrations. The Prl response following TRH administration was similar in both groups (delta max mean 49.5 +/- 12.5 SE and 49.4+/- 8.5 SE in normal and amenorrhoeic women, respectively). In contast, when release by sulpiride administration was studied the normal women had greater Prl release (delta max mean 169.9 +/- 18.2 SE) than amenorrhoeic women (delta max mean 99.8 +/- 9.4). Either the different oestrogen status (lower in amenorrhoeic women than in menstruating women) or the hypothalamic pituitary dysfunction likely to be responsible for the amenorrhoea in our patients, may explain the lower Prl release observed after sulpiride in subjects with amenorrhoea.