Objectives: Compare migraine duration with frovatriptan (versus baseline) in migraineurs reporting long- (24-72 h) or short-duration (524 h) migraines at baseline. Methods: Post hoc analysis of two postmarketing surveillance studies of migraineurs in German primary care clinics using frovatriptan (2.5 mg) to treat a single migraine attack. Using case-report forms, physicians recorded migraine characteristics at baseline (aura, duration, frequency, severity) and with frovatriptan (duration, severity, and recurrence). Patients and physicians rated frovatriptan effectiveness and tolerability versus previous therapy; physicians recorded adverse reactions. The primary analysis was change in migraine duration with frovatriptan versus baseline. Results: At baseline, 44.2% (7178/16 253) and 55.8% (9075/16 253) of patients reported short-and long-duration migraines, respectively; long-duration migraines were more often frequent (>= 3/months; 55.5% [4893/8811] vs. 30.6% [2132/6973]; p < 0.001; 95% CI, 23.5-26.5%), severe (61.7% [5584/9047] vs. 33.9% [2427/7156]; p < 0.001; 95% CI, 26.3-29.3%), and accompanied by aura (46.8% [4199/8977] vs. 31.3% [2215/7088]; p < 0.001; 95% CI, 14.0-17.0%). Mean (SD) onset of frovatriptan effect was <1 h; 72.3% (11 592/16 040) of patients required only one frovatriptan tablet. With frovatriptan, patients were 26.8-fold more likely to experience decreased versus increased headache duration (p < 0.001; 95% CI, 23.5-30.2) and 76.5% of patients reporting long-duration migraines at baseline experienced short-duration migraines. Most patients (87-90%) and physicians (70-75%) rated frovatriptan more effective and tolerable than previous therapies. Conclusion: Patients with more severe migraine characteristics at baseline were more likely to have attacks lasting >= 24 h. When using frovatriptan, patients were 26.8-fold more likely to experience decreased versus increased headache duration. Frovatriptan might be a good option for patients with long-duration or recurrent migraine attacks. The post hoc design and analysis of a single migraine attack are possible study limitations.