Résumé : Human african trypanosomiasis (HAT) is a major public health problem in several African countries. The Fontem focus is the second largest of the six major foci in Cameroon. Traditionally, HAT has been controlled by means of a vertical programme involving a mobile team which screens the population on a yearly basis: this programme is still in operation in the central and northern sectors of the focus. However, in the southern sector, a different approach, of a horizontal type, has been adopted. HAT screening has been integrated into a primary health-care programme, which is well accepted and supported by the community. The objective of this study was to compare the efficacy of the two approaches. Between 1983 and 1988, a total of 800 cases of HAT were notified in the Fontem focus; 732 patients were from the Fontem area, 333 in the sectors where the vertical programme is applied and 399 where the horizontal programme is applied. The efficacy of a programme is defined by its capacity to actively detect cases arising in the geographical area in which it is applied. On this basis, the horizontal programme is far more effective (85%) than the vertical programme (64%); the latter is also inconsistent over rime (30% in 1985) and unadapted to screening young adults (49% of 15 - to 29-year-olds). The efficacy of the vertical programme also diminishes with the distance from the town of Fontem where the mobile team is based. The horizontal programme diagnoses cases at an earlier stage and, as a result, the outcome is more favourable. The horizontal programme has offered the reference population excellent protection against HAT: during the study period, there were no registered deaths or encephalopathies due to HAT in the southern sector, whereas there were 12 deaths and six encephalopathies in the areas in which the vertical programme was applied. The horizontal approach therefore appears to give better results than the classical approach which aims to control severe out-breaks. However, it should be noted that the horizontal programme involves more sensitive and specific diagnostic techniques. On the basis of these results, it appears that the use of high-performance diagnostic methods within a primary health-care programme reaching a large fraction of the population, is highly suited to HAT screening.