Bone marrow aspirates are believed to provide a safer but less sensitive method in the diagnosis of visceral leishmaniasis (VL) compared with splenic aspirates. We examined the effect of the number of fields and the time of observation on bone marrow smear sensitivity and compared it to our experience with spleen aspiration. Bone marrow smears of 98 patients and splenic aspirates from 120 patients were examined. Among 87 patients with VL, the sensitivity of bone marrow aspirates was 40.2%, 65.5%, 89.7%, 92%, and 95.4% at 1, 5, 20, 30, and 60 minutes, respectively. The sensitivity of spleen aspirate examination was 93% for 114 patients. One patient died of shock after spleen aspiration. A bone marrow smear is very sensitive if examined thoroughly, reaching a sensitivity similar to that of spleen aspirate. We propose that a bone marrow smear be established as the technique of choice for the parasitologic diagnosis of VL.