The objectives of the present study were (1) to determine the prevalence rate of trypnnosomerninfections in the village cattle populations of Metekel district, North-west Ethiopia, (2) tornassess the prophylactic activity of isometnmidium chloride to natural trypanosome infectionsrnand (3) to monitor the trypanocidal activity of diminazene acelurate and isometamidiumrnchloride in mice experimentally infected with trypanosome field isolates.rnIn order to obtain information on the prevaknce rate of trypanosome infections in the area andrnto identify cattle herds highly suspected to be infected with drug resistant trypanosomernpopulations. questionnaire surveys and cross sectional studies were carried out from March tornOctober 1997 in four villages. The results of these studies showed that trypanosomosis is arnmajor constraint to livestock production in the area with an overall prevalence rate of 17.2%rn(95% CI: 14,20.8). Trypanosoma congolense was the dominant species accounting fo r 47.6%rnof the overall infections. The overall meanrn PCVrnvalue of the total cattle tested was found to bern4.9 ± 0.20% Parasitaemic cattle had significantly lower mean PCV values(21.6 + 0.47) thanrnaparasitaemic cattle (25.5±0.21 ) (p