1. The effects of cisplatin on renal microcirculation were evaluated in euvolemic Munich-Wistar rats submitted to micropuncture. Nine rats received a single dose of cisplatin (6 mg/kg, ip), and 6 control rats received the same volume (0.3 ml) of 150 mM NaCl 4 days before the measurements. 2. Cisplatin administration induced non-oliguric acute renal failure by decreasing glomerular filtration rate (GFR) from 0.96 +/- 0.05 to 0.33 +/- 0.04 ml/min (P less than 0.05) and by increasing urinary volume from 3.3 +/- 0.3 to 12.4 +/- 2.2 microliters/min (P less than 0.05). 3. Cisplatin administration decreased single nephron GFR from 34.2 +/- 2.1 to 20.1 +/- 2.3 nl/min (P less than 0.05) due to a reduction in both glomerular plasma flow from 106 +/- 9 to 61 +/- 6 nl/min (P less than 0.05) and transcapillary hydraulic pressure difference from 31 +/- 1 to 27 +/- 1 mmHg (P less than 0.05). An increase in arteriolar resistances, mainly afferent arteriolar resistance from 2.5 +/- 0.2 to 4.7 +/- 0.5 x 10(10) dyn.s.cm-5 (P less than 0.05), was observed. The glomerular ultrafiltration coefficient was unchanged.