Leukocytopenia and bacterial infections are common and serious complications in patients with AIDS. We report here on three patients in whom the administration of high IgG doses led to gradual (two patients) or prompt (one patient) increases in circulating leukocyte counts (from 200-600 to 2500-5900/microliters), inducing definite improvement in two patients; one patient died from Pneumocystis carinii pneumonia. Although the rise in leukocyte counts lasted for only approximately 3 weeks, high-dose IgG might be a useful therapeutic adjunct in such patients.