The parasitological techniques currently in use for the diagnosis of African trypanosomiasis were compared in a series of experiments for their capacity to detect Trypanosoma congolense, T. vivax and T. brucei in the blood of cattle. The darkground/phase contrast buffy coat method proved to be more sensitive than the haematocrit centrifugation technique, thick, thin and wet blood films in detecting T. congolense and T. vivax. On the other hand with T. brucei, mouse inoculation was the most sensitive method, followed by the haematocrit centrifugation technique. In a further series of experiments involving cattle infected with either T. congolense or T. vivax, the darkground/phase contrast buffy coat method was consistently more sensitive in detecting parasites than haematocrit centrifugation, capillary concentration using glycerol and miniature anion-exchange/centrifugation techniques. As well as showing superior sensitivity, the darkground/phase contrast buffy coat method allowed species identification, estimation of parasitaemia and simultaneous assessment of anaemia (packed red cell volume).