The renal toxicity of the extract of Polygalae Radix was investigated in rats. Rats were treated with 3.5 mg/Kg of the extract, i.p., for 7 days. Changes in consumatory behavior, 24 hour-urine and the activities of urinary enzymes were determined during the administration of the extract. Significant decrease in body weight and food consumption and increase in 24 hour-urine volume were observed during the administration. However, the quantity of total creatinine in urine was decreased significantly. Those indicate that subacute treatment with the extract might induce diuresis and the ditiresis might be due to the decrease in water reabsorption. In the activities of urinary enzymes, the activities of alanine aminopejotidase (AAP) and gamma-glutamyl transpeptidase (GGT) were increased 4.3 and 3.5 times and then returned to the control. The activity of N-acetyl-${eta}$-D-glucosaminidase (NAG) was increased 7.2 times and then decreased slowly. But, it was significantly higher than that of the control evea after the last administration. The activity of factate dehydrogenase (LDH) was increased continuozlsly during the treatment. It showed 32 times higher than the control. These results suggested that the extract of Polygalae Radix had toxic effect on kidney. Furthermore, the result suggested that the subacute administration of the extract induced resistance against the toxicity of Polygalae Radix.