This study was undertaken to compare the effectiveness and safety of three dosage levels of butorphanol in 52 patients with acute, severe migraine headache. After baseline evaluation, patients were given a dose of butorphanol 1.0, 2.0, or 3.0 mg intramuscularly on a double-blind basis. Assessments of pain intensity and pain relief using 100 mm linear analog scales (LAS), vital signs, and medication side effects were made at 15, 30, 45, and 60 minutes after the dose. All three treatment groups were similar in baseline characteristics. Each dose of butorphanol demonstrated a significant decrease in pain intensity LAS compared to baseline and increase in pain relief LAS over the observation period. The majority of analgesic response was observed at the first (i.e., 15-min) assessment. Doses of 2.0 and 3.0 mg produced significantly greater analgesia than did 1.0 mg at all posttreatment evaluations. No significant difference was apparent between the 2.0- and 3.0-mg doses. Adverse cardiovascular and respiratory depressant effects were not observed. An analgesic response to butorphanol 2.0 and 3.0 mg is clearly and rapidly evident and near maximum 30-45 minutes after administration. We conclude that in these doses butorphanol provides effective and safe analgesia for patients with acute migraine headache.