The efficacy and tolerability of oral sumatriptan (Imitrex tablets) were assessed in 187 migraineurs enrolled in a randomized, double-blind, parallel-group, placebo-controlled study. In the clinic, patients received oral sumatriptan 25 mg, 50 mg, or 100 mg, or placebo, for the treatment of a migraine attack. The results demonstrate that by 2 hours postdose, 52 to 57% of patients treated with sumatriptan 25 mg, 50 mg, 100 mg compared with 17% of patients treated with placebo achieved relief of headache (p < 0.05 for each sumatriptan group vs placebo). By 4 hours postdose, 65 to 78% of sumatriptan-treated patients compared with 19% of placebo-treated patients achieved relief of headache (p < 0.05 for each sumatriptan group vs placebo). Oral sumatriptan also effectively relieved nausea and photophobia and improved clinical disability. No serious or unusual adverse events were reported, and the pattern and incidence of adverse events did not vary among the sumatriptan doses. Each dose--25 mg, 50 mg, or 100 mg--of sumatriptan was effective and generally well tolerated.