The experiment was conducted to investigate the impact of hyperglycaemia on the trypanocidal efficacy of diminazene aceturate. Groups of alloxan-induced diabetic rats infected with T. brucei and T. congolense were treated with diminazene aceturate, and trypanocidal effects compared with normal non-diabetic controls. Results showed that the prepatent period was shorter in the diabetic (11.25±1.65 days) than non-diabetic-T. congolense (15.0±1.73 days), and also variations in responses to the trypanocidal therapy between the diabetic and non-diabetic groups were detected. Parasite clearance time did not differ significantly between the diabetic and non-diabetic (43.2±8.89 versus 52.8±8.89 hours in T. brucei and 33.6±5.9 versus 36.0±6.93 hours in T. congolense, respectively). The relapse intervals were shorter in the diabetic than non-diabetic (16 days versus 23 days in T. brucei, and 7 days versus 14 days in T. congolense, respectively). Proportion of relapses was greater in the diabetic- (100%) than non-diabetic-T. congolense (66.7%). We also find parasite species-related differences in susceptibility to the trypanocide, with a higher apparent cure rate in the T. brucei than T. congolense group. We conclude from the results of this study that the chemotherapeutic effectiveness of diminazene aceturate may be diminished in patients with diabetes mellitus. Further study is needed to validate this hypothesis.