Three types of human leishmaniases are known to occur in Kenya: visceral leishmaniasis, caused by Leishmania donovani, and cutaneous leishmaniasis caused by L. aethiopica and L. major. Visceral leishmaniasis is the most important of the three in eastern Africa, not only because it is fatal but also because several epidemics have occurred periodically since the disease appeared in the country about 40 years ago resulting in many deaths. L. aethiopica and L. major are chiefly zoonotic and people contract the disease when they wander into areas containing animal reservoirs and infected vectors. Control measures were undertaken against vectors and reservoirs during an epidemic outbreak of kala-azar in Machakos District.