This study investigated the peroxidative state of renal failure by measuring lipid peroxidation. The generation of lipid peroxides by rat hepatic microsomes was compared between experimental renal failure caused by 7/8 nephrectomy and healthy control animals. The concentrations of BUN at the point of sacrifice were 84.2 +/- 18.4 (mean +/- SD) in nephrectomized and 19.8 +/- 4.3 mg/dl in the control group (p < 0.01, n = 5). Microsomal generation of thiobarbituric acid reactive substance was 31.2 +/- 2.8 in the nephrectomized group and 20.9 +/- 4.9 nmol/incubation/min in the control group. There was a significant difference between the groups (p < 0.01, n = 5). In summary, the generation rate of lipid peroxides in the microsomes obtained from the rats with experimental renal failure was significantly higher than the control. This study confirms an increased peroxidative state, and specifies one of the sites of increased lipid peroxide generation in renal failure.