The control of Trypanosoma rhodesiense sleeping sickness by clinical methods is often complicated by the existence of animal reservoir hosts which greatly contribute to the persistence of the disease in many parts of East Africa. The control of sleeping sickness should, therefore, include control of the vector and elimination of the reservoir hosts. Another factor which is often ignored, when planning sleeping sickness control measures, is the influence of cultural practices of the resident human population on the epidemiology of the disease in any given location in East Africa. At Lower Kitete, northern Tanzania, trypanosomiasis due to T. rhodesiense is occupational in nature so that many of the individuals are infected in Lossitete Forest while engaged in various activities. The factors favouring infection within the area, and the role played by the cultural practices of the Masai around the area in bringing about the outbreak of an epidemic, are discussed. The importance of understanding the cultural practices and occupational tendencies of the Masai in Lower Kitete, where trypanosomiasis outbreaks have occurred in the last 10 years, is stressed. With such an understanding the management of trypanosomiasis at Lower Kitete may be successful.