To evaluate the renal toxicity of the antitumor agent, 1-(N-methyl) piperazinyl-3-phenyl-isoquinoline(CWJ-$alpha$-5), rats were terated with CWJ-$alpha$-5 (acute : 100mg/kg, i.p., single and subacute : 10mg/kr, i.p., daily for 7 days). The changes in the body weights, water consumption, kidney weights and urine volume after and during the treatment were observed. The concentrations of urinary creatinine, the activities of N-acetyl-$eta$-D-glucosaminidase (NAG), alanine aminopeptidase (AAP), $gamma$-glutamyl transpeptidase ($gamma$-GT) and lactate dehydrogenase (LDH) in 24 hr urine were also determined. The body weight and water consumption were decreased after the acute and subacute administration. However, the excretion of urine was not changed except the 1 day after the acute treatment. The excretion of creatinine was significantly decreased from 1 day after acute administration and continuously decreased. Also the excretion of creatinine was decreased during subacute administration. However, the protein excretion did not changed in both treatment. Those indicate that CWJ-$alpha$-5 might decrease the metabolic rate of muscle. The urinary activities of NAG, AAP, $gamma$-GT, and LDH were significantly affected by the drug treatment. The urinary activities of NAG, AAP and $gamma$-GT were significantly increased 1 and 3 days after the acute administration and then returned to the control value. However, the urinary activities of LDH were increased 7 days after acute treatment. During subacute treatment, the urinary activities of $gamma$-GT were not changed. However, the urinary activities of NAG, AAP and LDH were only significantly increased after the third administration. These results indicate that either the high acute dose or the subacute administration with low dose of the compound might induce a temporal damage in the kidney cells.