Six hundred and ninety-three patients with kala-azar were seen in Khartoum, Sudan, from January 1989 to February 1990. They were almost exclusively from the Nuer tribe, originating from the western Upper Nile province in southern Sudan, an area not known previously to be endemic for kala-azar. Because of the civil war in southern Sudan no treatment was available locally and massive migration to northern Sudan occurred; many died on the way. All age groups were affected; there was a slight male preponderance (56%). In the clinical presentation, marked generalized lymphadenopathy was prominent (84%). Splenomegaly was absent in 4% of cases. Patients usually showed anaemia, leucopenia and/or thrombocytopenia. 623 patients were treated with sodium stibogluconate, 10 mg/kg for 30 d; relapse occurred in 4% and death in 12%. Latterly, 70 patients were treated with sodium stibogluconate at 2 x 10 mg/kg for 15 d, with relapse in 6% and death in 6%. The difference between the 2 regimens in the number of relapses and deaths was not significant. The outbreak may have been caused by a combination of factors: the introduction of the parasite from an endemic area to a non-immune population, the presence of malnutrition caused by loss of cattle and unavailability of other food sources, and possibly an ecological change in favour of the sandfly vector.