Ivermectin is an anthelmintic agent that has been a safe, effective treatment for onchocerciasis (river blindness) when given in a single oral dose of 150 to 200 micrograms per kilogram of body weight. Anecdotal reports of improvement in patients who suffered from infestation with the mite Sarcoptes scabiei suggest that the ectoparasitic disease scabies might be treated with ivermectin.We conducted an open-label study in which ivermectin was administered in a single oral dose of 200 micrograms per kilogram to 11 otherwise healthy patients with scabies and to 11 patients with scabies who were also infected with the human immunodeficiency virus (HIV), 7 of whom had the acquired immunodeficiency syndrome. All patients received a full physical and dermatologic examination; scrapings from the skin of all patients tested positive for scabies. Patients were reexamined two and four weeks after treatment, when the scrapings for scabies were repeated. The patients used no other scabicides during the 30 days before ivermectin treatment or during the 4-week study period.None of the 11 otherwise healthy patients had evidence of scabies four weeks after a single dose of ivermectin. Of the 11 HIV-infected patients, 2 had or = 50 lesions, and 2 had heavily crusted skin lesions. In eight of the patients the scabies was cured after a single dose of ivermectin. Two patients received a second dose two weeks after the first. Ten of the 11 patients with HIV infection (91 percent) had no evidence of scabies four weeks after their first treatment with ivermectin.The anthelmintic agent ivermectin, given in a single oral dose, is an effective treatment for scabies in otherwise healthy patients and in many patients with HIV infection.