Rizatriptan is a potent, oral, 5‐HT 1B/1D agonist with more rapid absorption and higher bioavailability than oral sumatriptan. It was postulated that this would result in more rapid onset of effect. This randomized, double‐blind, triple‐dummy, parallel‐groups study compared rizatriptan 5 mg, rizatriptan 10 mg, sumatriptan 100 mg, and placebo in 1268 outpatients treating a single migraine attack. Headache relief rates after rizatriptan 10 mg were consistently higher than sumatriptan at all time points up to 2 hours, with significance at 1 hour (37% versus 28%, P =0.010). All active agents were significantly superior to placebo with regard to headache relief and pain freedom at 2 hours ( P ≤0.001). The primary efficacy endpoint of time to pain relief through 2 hours demonstrated that, after adjustment for age imbalance, rizatriptan 10 mg had earlier onset than sumatriptan 100 mg ( P =0.032; hazard ratio 1.21). Rizatriptan 10 mg was also superior to sumatriptan on pain‐free response ( P =0.032), reduction in functional disability ( P =0.015), and relief of nausea at 2 hours ( P =0.010). Significantly fewer drug‐related clinical adverse events were reported after rizatriptan 10 mg (33%, P =0.014) compared with sumatriptan 100 mg (41%). We conclude that rizatriptan 10 mg has a rapid onset of action and relieves headache and associated symptoms more effectively than sumatriptan 100 mg.