A 48-year-old male was referred to our university hospital for severe azotemia with muscle cramp. He had been taking Chinese herbs as a traditional medicine to reduce hyperuricemia for about 9 months. Urinalysis showed trace proteinuria and hematuria without any casts. Renal glucosuria was also observed. In addition to azotemia, hyperchloremic metabolic acidosis and severe anemia were revealed. Hemodialysis was conducted and his general condition improved. A renal biopsy specimen revealed severe interstitial fibrosis and tubular atrophy with cellular degeneration. No remarkable glomerular changes were observed except for wrinkling of the basement membrane in a few glomeruli. Aristolochic acid was detected in the Chinese herbs, leading to the diagnosis of aristolochic acid nephropathy (AAN). His renal dysfunction was considered to be irreversible and he underwent maintenance hemodialysis. In Japan, AAN or Chinese herbs nephropathy decreased after an outbreak from 1995 to 2000. The public should be warned again that Chinese herbs, which are not permitted by the Japanese government, may contain aristolochic acid.