A new renal disease called 'Chinese-herb nephropathy' (CHN) has been reported to occur in women who have ingested slimming pills containing powdered extracts of the Chinese herb Stephania tetrandra (ST). Moderate to end-stage renal disease developed, requiring renal replacement therapy by dialysis or transplantation. Phytochemical analyses of the pills revealed the presence of aristolochic acids (AA) instead of tetrandrine, suggesting the substitution of ST (Han fang ji) by Aristolochia fangchi containing nephrotoxic and carcinogenic AA. A typical histological feature of CHN is a progressive interstitial fibrosis leading to a severe atrophy of the proximal tubules, as documented by the urinary excretion rates of markers of tubular integrity (reduction of neutral endopeptidase enzymuria and high levels of microproteinurias). Removal of the native kidneys and ureters in end-stage CHN patients provided a high prevalence of urothelial carcinoma (46%). Tissue samples contained AA-related DNA adducts, which are not only specific markers of prior exposure to AA but are also directly involved in tumorigenesis. Exposure to Aristolochia species (spp.) is associated with the development of renal interstitial fibrosis (CHN) and urothelial cancer in humans. Health professionals should be aware that in traditional Chinese medicine, Aristolochia spp. are considered interchangeable with certain other herbal ingredients and are also sometimes mistaken for ST, Akebia, Asarum, Clematis spp. and Cocculus spp. in herbal remedies.