The pathologic changes induced by Cis-platinum (II) diamminedichloride (CPDD) therapy in the kidneys are described in 12 patients with solid tumors and malignant lymphomas. According to dosage of CPDD the patients were divided into two groups: 1) low-dose group--.0.5-2 mg/kg daily, for 1 to 6 days; and 2) high-dose group--single injection of 3 or more mg/kg with concommitant mannitol-induced diuresis. Pathologic changes in the kidneys were essentially similar in both groups and consisted of focal acute tubular necrosis, affecting primarily the distal convoluted tubules and collecting ducts, dilatation of convoluted tubules, and formation of casts. These changes persisted as long as 29 days post CPDD therapy. In addition, the collecting ducts exhibited significant epithelial atypia. BUN and serum creatinine levels were elevated in both groups. The mean BUN/serum creatinine values were 54/2.2 mg/100 ml and 32/2.0 mg/100 ml for low and high-dose groups, respectively. Since the nephrotoxicity of CPDD is known to be dose-related, our findings suggest that mannitol-induced diuresis has considerably decreased the renal toxic damage of CPDD therapy in these patients.