Dihydroergotamine mesylate (DHE), an ergot alkaloid, has been extensively utilized and studied in the treatment of episodic and chronic migraine. This article reviews the pharmacokinetics, pharmacodynamics, and clinical efficacy and safety of DHE, particularly in comparison to ergotamine tartrate (ET), a similar ergot alkaloid with a long history of use in the treatment of migraine. Structural differences between these 2 compounds account for clinically important distinctions in their pharmacokinetic, pharmacodynamic, and adverse event profiles. DHE is a significantly less potent arterioconstrictor than is ET, which makes it a potentially much safer drug. In addition, DHE is associated with a markedly lower incidence of medication-withdrawal headache, nausea, and vomiting than is ET. The safety and efficacy data presented here are derived from clinical trials and case series involving DHE administered by intravenous infusion, intramuscular or subcutaneous injection, or intranasal spray.