In this double-blind study, the efficacy and tolerability of a single dose of almotriptan (6.25 or 12.5 mg) was compared with placebo in the treatment of three consecutive migraine attacks of moderate or severe intensity. Of 1013 randomized patients, 722 evaluable patients completed the study. The total number of attacks relieved (severe or moderate pain reduced to mild or no pain) at 2 h post-dose was significantly higher (P < 0.001) after treatment with almotriptan 6.25 or 12.5 mg compared with placebo (60% and 70% vs. 38%, respectively). Moreover, a consistent response was achieved across and within patients for almotriptan 6.25 or 12.5 mg compared with placebo (pain relief in at least two out of three attacks within 2 h for 64% and 75% vs. 36%, respectively) and less than one-third of the patients relapsed within 24 h. Almotriptan was well tolerated with no significant differences between the almotriptan and placebo treatment groups in the percentage of patients reporting adverse events. Overall, the 12.5-mg dose was associated with the most favourable efficacy/tolerability ratio and is, therefore, the recommended dose.