A 21 year old female treated for recurring gastric troubles with dopamine-antagonists (domperidone, metoclopramide) developed a clinically manifest hyperprolactinemia (3055 microU/l; normal value < 650 microU/l) with galactorrhea only two days after a new two day course of metoclopramide. The drug was withdrawn and within days mastodynia and galactorrhea subsided. A control of plasmatic prolactin two weeks later yielded a normal value (358 microU/l). After administration of metoclopramide or domperidone hyperprolactinemia is regularly observed and galactorrhea has been described earlier. It is unclear why this patient inspite of repeated administration of one dopamine antagonist remained asymptomatic whereas the other after a short time and only a few doses led to galactorrhea. It is conceivable that differences in passage into the cerebrospinal fluid or the better penetration of the blood-brain barrier favored the development of galactorrhea under metoclopramide. This case served to discuss the pathophysiologic background of drug-induced hyperprolactinemia.