Twenty-four Kenyan patients with visceral leishmaniasis were treated for 30 days with either conventional therapy (daily pentavalent antimony, n = 14) or experimental immunochemotherapy (daily antimony plus interferon-gamma [IFN-gamma] every other day, n = 10). All 24 patients responded clinically to treatment, and microscopic splenic aspirate scores rapidly decreased in both groups. As judged by splenic aspirate culture results, IFN-gamma-treated patients responded more quickly (50% versus 22% culture-negative after one week and 75% versus 58% culture-negative after two weeks). While not statistically significant, these differences raise the possibility that combination therapy using IFN-gamma, which was safe and well-tolerated, may accelerate the early parasitologic response in patients with visceral leishmaniasis.