The protective effect of Hachimi-jio-gan extract against chronic renal failure in a subtotal nephrectomy rat model was investigated. The level of serum urea nitrogen by nephrectomy was increased over 15 weeks, but the administration of Hachimi-jio-gan at 50 and 200 mg led to the decrease. In addition, the levels of creatinine (Cr), urinary methylguanidine (MG) and MG/Cr were increased, whereas Cr clearance dramatically decreased in nephrectomized rats. However, oral administration of Hachimi-jio-gan extract prevented the elevation of these uremic toxins in serum and urine, and the production of hydroxyl radical. Moreover, nephrectomy led to a significant decline in superoxide dismutase (SOD) and catalase activities, but increased glutathione peroxidase activity compared with normal levels, indicating an abnormal antioxidative system. The increased activity of both SOD and catalase by the oral administration of Hachimi-jio-gan suggested that these enzymes are associated with the protective role of Hachimi-jio-gan extract against oxidative stress by nephrectomy. Moreover, the decrease in serum albumin in nephrectomized control rats was increased and proteinuria was ameliorated by the administration of Hachimi-jio-gan with improved glomerular hyalinosis, interstitial fibrosis and inflammation, suggesting the beneficial effect of Hachimi-jio-gan to prevent glomerular sclerosis and progressive renal fibrosis. This study suggests that Hachimi-jio-gan plays a protective role in the progression of chronic renal failure through the decline in uremic toxins, elevation of antioxidative enzyme activity such as SOD and catalase, and amelioration of histopathological lesions in the kidney.