Studies were designed to determine the cause of the reduced glomerular filtration rate (GFR) in early cisplatin-induced acute renal failure. Rats were studied 72 h following a single intraperitoneal injection of cisplatin (5 mg/kg) or vehicle (0.9% NaCl). Whole kidney GFR and blood flow were lower in cisplatin-treated animals than in controls (0.30 +/- 0.06 vs. 1.17 +/- 0.06 ml X min-1 X g kidney wt-1 and 5.30 +/- 0.62 vs. 8.25 +/- 0.43 ml X min-1 X g kidney wt-1, respectively; P less than 0.001), as were superficial nephron GFR and stop-flow pressure (20.2 +/- 2.1 vs. 34.5 +/- 2.0 nl X min-1 X g kidney wt-1 and 29.0 +/- 1.9 vs. 39.8 +/- 1.3 mmHg, respectively; P less than 0.001). After volume expansion, renal plasma flow increased in control rats, whereas whole kidney and single nephron GFR did not change. In experimental animals, whole kidney filtration rate rose to 0.58 +/- 0.07 ml X min-1 X g kidney wt-1, single nephron filtration rate increased to 29.9 +/- 3.5 nl X min-1 X g kidney wt-1 (P less than 0.005), and renal plasma flow increased to 5.62 +/- 0.60 ml X min-1 X g kidney wt-1 (P less than 0.05). Intratubular hydrostatic pressure was not different in the two groups before or after volume expansion. The results of these studies show that the reduced GFR in early cisplatin-induced renal failure is due, in part, to reversible changes in renal blood flow and renal vascular resistance.