1. Several haematological and biochemical parameters were measured in the erythrocytes of the grey-headed fruit bat. 2. The level of 2,3-diphosphoglycerate was almost twice that found in human erythrocytes. Similarly pyruvate kinase activity was more than twice that of man. 3. The activities of other enzymes of the glycolytic pathway were similar to those found in man. 4. The level of reduced glutathione (GSH) and the GSH regeneration rate in the erythrocytes of the bat were comparable to those found in man.