A 69-year-old woman underwent hysterectomy with partial resection of left ureter for uterus cancer and ureterosigmoidostomy in 1960. She suffered remittent pyelonephritis in 1991, and her left kidney was removed for hydronephrosis the following year. She was admitted to our hospital for treatment of colon cancer in 1997. Colonoscopy and barium enema study showed a round tumor in the sigmoid colon, which was 4cm in diameter and almost occluded the lumen. Sigmoidectomy was performed. The tumor occupied the anal side of the ureterosigmoidostomy, which was well-differentiated adenocarcinoma limited to proper mucosa histologically. In conclusion, patients with ureterosigmoidostomy are a high-risk group for colon cancer, and need careful long-term follow-up with colonoscopy.