The effects of experimental anaemia on the levels of reduced glutathione (GSH) and the activity of glycolytic enzymes in the erythrocytes of normal and GSH-deficient Merino sheep were investigated. There was a rise in red cell GSH levels in both groups of sheep; the magnitude of this response was, however, quite different. When expressed as a percentage of the initial value, the rise in GSH level was 18 % in normal and 263 % in GSH-deficient animals. There was also an increase in the activities of various enzymes following phlebotomy but this increase was similar in the two groups of sheep.