The objective of this study was to determine the effects of oral sumatriptan on growth hormone (GH) release throughout the menstrual cycle in healthy female volunteers. A placebo-controlled cross-over design was employed. Subjects were tested a total of six times over two consecutive menstrual cycles; twice in the early follicular phase, twice in midcycle and twice in the late luteal phase. Oral sumatriptan (100 mg) and placebo were administered on alternate visits. Twelve healthy female volunteers aged between 18-40 years with regular menses and not taking oral contraceptives were recruited. Baseline blood samples at 0 min were taken for GH, oestrogen and progesterone estimation. G H was measured at +60, +90, + 120 and + 180 min following administration of oral sumatriptan 100 mg or matched placebo. GH, progesterone and oestrogen were measured by radioimmunoassay. At each phase of the menstrual cycle serum GH levels peaked at 60-90 min following administration of oral sumatriptan compared to placebo which showed no response. Analysing GH response to sumatriptan and placebo over time for the three phases of the menstrual cycle (three-way ANOVA) demonstrates that the G H response to sumatriptan did not alter.