The review describes an explanation of the molecular mechanism of a unique type of renal fibrosis, designated as Chinese herbs nephropathy (CHN). So far, over 100 patients have been identified, all of them followed a slimming regimen with the prolonged use of Chinese herbs. Using the ³²P-postlabelling method, three specific DNA adducts derived from aristolochic acids (AA) were detected in renal tissues of patients with CHN. The AA-specific adduct pattern was also found in a ureter obtained from a CHN patient after renal transplantation. The data indicate that AA are involved in CHN providing an explanation for the increasing number of urothelial carcinomas reported in patients with CHN.