In a pilot trial, 28 days of oral treatment with 100-200 mg miltefosine (hexadecylphosphocholine) per day cured 14 of 15 patients with Indian visceral leishmaniasis (VL). To extend the testing of this regimen, 45 additional subjects with VL, of whom 17 had failed previous antimony therapy, were treated with 100 (N = 17), 150 (N = 18) or 200 (N = 10) mg/day. Enrollment at 200 mg/day was stopped after three subjects in this treatment arm developed reversible but serious (grade-3) adverse reactions. The overall clinical and parasitological responses to miltefosine were rapid, with 40 [89%; 95% confidence interval (CI) = 76%-96%] and 44 (98%; CI = 88%-100%) of the patients apparently cured on days 14 and 28, respectively. The one 'treatment failure' recorded on day 28 (and at 6 months) was a subject lost to follow-up. Those apparently cured by day 28 included six patients (one on 100 mg, two on 150 mg and three on 200 mg/day) removed from treatment on days 7-17 because of grade-3 diarrhoea (two cases), vomiting (two cases), diarrhoea and hepatotoxicity (one case) or nephrotoxicity (one case). Transient, mild-moderate vomiting and/or diarrhoea were common during weeks 1-2 and about 25% of the patients also developed primarily mild, self-limited increases in concentrations of aspartate aminotransferase and creatinine and/or blood urea nitrogen. At a 6-month follow-up, all 44 patients apparently cured at day 28 were considered complete responders (definitive cures), including the six treated for only 7-17 days. These results indicate that 100 mg miltefosine/day for 28 days is a promising oral-treatment regimen for VL cases, including those with antimony-unresponsive infections.