The effect of a one month treatment with flunarizine (5 mg/day) on pituitary responsiveness to gonadotrophin-releasing hormone (GnRH), thyrotrophin-releasing hormone (TRH) and arginine infusion was assessed in 17 adolescents (11 M, 6 F) treated with the drug to prevent migraine attacks. Basal prolactin concentrations as well as the prolactin response to TRH were significantly (p less than 0.05) increased after flunarizine treatment. Flunarizine had no effect on the folliclestimulating and luteinising hormone response to GnRH stimulation, growth hormone response to arginine infusion or thyrotrophin response to TRH stimulation. Our data suggest that flunarizine may interfere with the hypothalamic-pituitary-prolactin axis decreasing dopaminergic inhibitory tonus.