During the serial attempts to identify the chemical and biological characteristics of Ailanthi Cortex Radicis, the root bark of Ailanthus altissima (Simaroubaceae), we find out the serious toxic effect on kidney by chloroform fraction of the methanolic extract of the herb drug. The toxicities were revealed as the increase of urea nitrogen amount in blood and lactate dehydrogenase and ${gamma}-glutamyltransferase$ activities in urine and the decrease of the concentration of glutathione and both of protein bound and non-protein bound -SH in kidney tissue.