Several parenteral drugs appear to be effective for the treatment of acute migraine. The evidence supporting their efficacy is, however, limited by the small number of placebo comparisons; the small size of most trials; and the diversity of settings, diagnostic criteria, and outcome measures used. The inconclusive comparisons among classes of drugs and individual agents suggest that the choice among parenteral alternatives for the treatment of acute migraine may, for the present, depend more on side effects and contraindications than on data about efficacy.