Haemolysis is the most prominent pathogenic cause of the anaemia in trypanosomosis. Haemolytic anaemias are normally accompanied by increased erythropoiesis, reticulocyte response and increase in the mean corpuscular volume of circulating erythrocytes. In trypanosomosis, the anaemia is accompanied by inadequate erythropoiesis. This is suggested by suboptimal reticulocyte response in infected rodents, little or no reticulocyte response in infected ruminants and weak erythrogenic capacity of infected sheep plasma in mice. The mean corpuscular volume increases in the acute phase reaching a peak at 3 to 4 weeks after infection and drops to normal or below normal in the chronic phase; suggesting that erythropoiesis moderately increases in the acute phase but Wanes and becomes completely depressed as the disease progresses into the chronic phase. The causes of the dyserythropoiesis are meanwhile not clear but may be found to be associated with erythroid injury, depressed erythropoietin synthesis and bioactivity or depressed haemoglobin synthesis or their interplay. Extensive studies in these areas are still necessary.