The present study was designed to investigate the early hemodynamic and tubular effects of cisplatin administration on dogs. To localize the nephrotoxic actions of cisplatin, we have taken advantage of the lithium clearance method. After infusion of 5 mg of cisplatin per kg, an immediate and significant increase in urinary flow rate (from 0.39 +/- 0.07 ml/min to 0.73 +/- 0.12 ml/min), sodium clearance (from 0.33 +/- 0.11 ml/min to 0.65 +/- 0.14 ml/min), potassium clearance (from 9.23 +/- 0.48 ml/min to 10.77 +/- 0.95 ml/min), lithium clearance (from 15.55 +/- 2.21 ml/min to 23.76 +/- 4.00 ml/min) and fractional lithium clearance (from 0.31 +/- 0.03 to 0.44 +/- 0.04) was seen. This occurred without measurable changes in glomerular filtration rate and renal blood flow. The calculated fractional as well as absolute rates of proximal reabsorption of sodium decreased significantly from 0.68 +/- 0.03 to 0.56 +/- 0.04 and from 4.76 +/- 0.32 mmol/min to 3.92 +/- 0.23 mmol/min, respectively. The results show that administration of cisplatin causes an acute, mainly proximal tubular impairment in dogs without alterations in renal hemodynamics.