The efficacy and safety of three regimens of treatment for kala-azar (visceral leishmaniasis) with sodium stibogluconate were evaluated in a randomised clinical trial to ascertain the optimal duration of treatment for Indian patients. The study included a total of 312 (226 male, 86 female) patients with fresh kala-azar, confirmed by demonstration of parasites in aspirates from bone marrow or spleen, who were randomly allocated into three treatment groups of 104 patients in each to receive sodium stibogluconate intramuscularly. The dose of the drug was 20 mg/kg/body weight/daily with a maximum of 8.5 ml for 20, 30 and 40 days (groups A, B, C respectively). The response of treatment was assessed under blind conditions and patients were followed up each month for a period of six months. The number of patients who were apparently cured (i.e., those whose temperature had returned to normal at the end of their respective regimen and aspirates were free of parasites) was 91 (87%) in group A, 98 (94%) in group B, and 102 (98%) in group C. The difference between groups A and C was significant (P less than 0.01). The number of patients who were ultimately cured at six months was 74 (71%) in group A, 86 (83%) in group B and 98 (94%) in group C. These patients had not relapsed and were cured as confirmed by a bone marrow aspirate which was free of parasites. The difference between groups A and C (P less than 0.001) and groups B and C (P less than 0.05) were significant. However, the difference between groups A and B was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)