We evaluated the effect of l-deprenyl, a drug that increases the availability of endogenous dopamine, on the plasma levels of prolactin and growth hormone in 10 female patients with migraine and in 10 control subjects matched for age and menstrual phase. The patients showed a significant decrease in prolactin levels at 30, 60 and 120 min after the oral administration of 5 mg of l-deprenyl when compared with the values obtained in controls (p < 0.001). The effects of l-deprenyl on growth hormone plasma levels were not significantly different between patients and controls. These data suggest that l-deprenyl inhibits prolactin release in migraine patients, but not in control subjects. This differential sensitivity could be explained by dopamine receptor supersensitivity in migraine patients.