Renal and electrolyte disturbances in 91 patients with chronic myelogenous leukemia (CML) were analyzed over a period of these twenty years. At diagnosis, renal and electrolytes were studied in 72 patients including 65 in chronic cases, 5 in accelerated phase and 2 in blastic crisis. There were 8 cases of hypocalcemia among 62 patients and 5 cases of hyperphosphatemia among 48 patients. The cases of hyperphosphatemia and renal dysfunction had short median survival. There were no significant differences of renal and electrolyte disturbances between before and after chemotherapy. Various electrolyte disturbances, that is, hyponatremia, hypo-, hyperkalemia, hypocalcemia, hypo-, hyperphosphatemia, were found in the blastic crisis of CML. In the last admission, renal dysfunction and various electrolyte disturbances were present in almost half of the cases. Pathological studies were performed in 18 autopsy cases. Acute tubular insufficiency or necrosis, hypercalcemic nephropathy, and renal infiltration of leukemic cells were recognized in patients who had renal dysfunction.