We have studied the granulocyte reserve of bone marrow (ethiocholanolone test), the morphological aspects and the mitotic index of the granulopoietic line in 10 patients undergoing long-term haemodialysis. The granulocyte reserve was reduced in 7 cases. This phenomenon is probably due to the granulocyte loss which occurs in dialysis. The granulopoietic cells showed cytoplasmatic vacuolisation and lysis of chromatin. The mitotic index was at the upper limits or above.