Within the last decade our understanding of the pathophysiologic mechanisms which generate migraine has expanded considerably. Accompanying these advances in basic science, new agents designed to treat migraine acutely have exhibited unprecedented pharmacologic selectivity and clinical efficacy. While these abortive agents clearly can provide many migraine patients with a degree of headache control they previously have not enjoyed, such treatment typically will not provide lasting benefit to individuals whose headaches are more pervasive and may require stabilization through effective prophylactic therapy. Unfortunately, our arsenal of agents for migraine prophylaxis has not grown as rapidly as that of the abortive medications, and for the most part clinicians and patients are left to rely upon a small handful of “traditional” drugs for that purpose. One notable exception to this is divalproex sodium; the safety and efficacy of this new agent for migraine prevention have been documented consistently in a series of recent clinical trials.