Long-acting somatostatin analogue (SMS 201-995) inhibits serotonin, bradykinin, prostaglandins, substance P, and vasoactive intestinal peptide, which may be involved in migraine. We therefore decided to test the efficacy of SMS 201-995 in relieving the pain of acute migraine attacks. Headache relief was defined as a reduction in severity from grade 3 or 2 (severe or moderate) to 1 or 0 (mild or none). Patients experiencing migraine attacks were evaluated clinically. A double-blind parallel group trial was performed in which patients randomly received either a subcutaneous injection of placebo (saline) or SMS 201-995 (100 micrograms). SMS 201-995 was significantly more effective than placebo in reducing headache grade at 2 h (1.5 +/- 0.6 vs 2.2 +/- 0.7; p < 0.01), 4 h (1.5 +/- 0.6 vs 2.1 +/- 0.8; p < 0.05) and 6 h (0.8 +/- 0.9 vs 2.1 +/- 0.8; p < 0.001) after the initiation of treatment. By 6 h, apparent headache relief (reduction in severity from grade 3 or 2 to 1 or 0) was experienced in 76.5% of SMS 201-995 treated patients and 25% of the placebo-treated group. Headache relief was significantly better in patients taking SMS 201-995 (p < 0.02). Furthermore, none of the patients became pain-free (headache grade 0) on placebo, while significantly more patients (47%) were pain-free on SMS 201-995 at 6 h (p < 0.01). Headache improvement started significantly earlier in those patients treated with SMS 201-995 than with placebo. SMS 201-995 significantly improves the pain of migraine attacks, 2 h after the beginning of treatment. Additionally, we observed no side effects of SMS 201-995. We therefore conclude that a single dose of 100 micrograms given subcutaneously is an effective and well-tolerated agent for the treatment of migraine attacks.