Drug resistant trypanosome infections in livestock have been Reported from 13 sub-Saharan countries so far, in eight of which multiple resistance occurs. Since new trypanocides are unlikely to appear on the market in the near future, information about the occurrence, extent and impact of drug resistant trypanosome infections in livestock becomes increasingly important for the planning and implementation of effective trypanosomosis and tsetse control strategies in the affected areas. This paper presents the results of a field study which aimed to assess the therapeutic and prophylactic activity of ISMM (Isometadium) in Trypanosoma spp. infected dairy cattle in 1994 in an endemic area, Mukono country in Uganda. The paper discusses PCR for the detection of treatment failure and the suitability for drug resistance screening under field countries.