• Naproxen sodium is an inhibitor of platelet aggregation and prostaglandin synthesis and is also a potent anti-inflammatory agent. Because of these properties, it was evaluated in prophylaxis of migraine by a double-blind, placebo-controlled crossover study in 34 patients. Drug "preference" and therapeutic effect were rated by both patient and investigator. Overall, both preferred drug over placebo. An index of migraine activity was calculated from a daily record kept by the patient; it demonstrated a significant reduction in headache severity, duration, disability, and medication needed. Adverse effects were minimal and similar in drug and placebo. Naproxen is a promising agent in the prophylaxis of migraine.