We sought a drug for the killing of Dracunculus medinensis, infection with which is endemic to more than two-thirds of India. Patients with blebs and palpable worms were treated, as we wished to kill the worm before it discharged larvae. Niridazole (Ambilhar®)—25 mg per kg body weight daily—was administered to 36 Indian villagers and to 20 hospitalized persons. Remission of symptoms of dracunculiasis, with extrusion of the worm, occurred in all but six patients. Side-effects, principally gastrointestinal disturbances and headache, did not warrant discontinuation of the drug. Many villagers, however, stopped treatment, owing to suspicion and refusal to tolerate side-effects. Niridazole killed adult worms, resulting in the healing of the acute lesions of dracunculiasis; protected water supplies must, however, accompany chemotherapy for eradication of the disease.