Using a randomized study, we compared a daily and an alternate-day regimen of amphotericin B for the treatment of kala-azar, with respect to efficacy, adverse reactions, cost-effectiveness, and tolerance. The study subjects were 80 kala-azar patients, drawn from the first four decades of life and matched by age, sex, and parasite load. The patients were randomly allocated to treatment groups A and B (40 patients per group). Patients in group A received a daily regimen of amphotericin B, starting with an escalating dose of 0.05 mg/kg body weight per day until a daily dose of 1 mg/kg was reached; the latter dose was then given daily till a total dose of 20 mg/kg body weight had been administered. The patients in group B also started with an escalating dose of 0.05 mg/kg but when 1 mg/kg was reached the drug was given on alternate days. All 80 patients using the two treatment regimens were cured, no patient relapsed in either group in 6 months of follow-up, and their bone-marrow aspirates were free of amastigotes. Treatment of kala-azar patients with the daily regimen of amphotericin B at a dose 1 mg/kg body weight was as effective, not more toxic, equally well tolerated, and much more cost-effective than the alternate-day regimen and should be adopted for treatment of this condition.