To evaluate the nephrotoxicity of cisplatin, serum levels of sodium, potassium, chloride, calcium, phosphorous, magnesium, BUN, creatinine and creatinine clearance were measured before and after administration of cisplatin in 18 cases of patients with malignant neoplasm. The results were as follows : 1) Serum calcium, magnesium, potassium and BUN levels were changed after cisplatin administration, but those changes were not statistically significant. 2) The mean value of creatinine clearance was not decreased significantly after treatment with cisplatin. 3) Acute renal failure was developed in one case, and four cases of hypocalcemia, hypomagnesemia were also detected after administration of cisplatin.