We report a rare case ofrectal neuroendocrine carcinoma(NEC)following sigmoidectomy of sigmoid colon cancer. NEC of the rectum is a rare disease. It has an extremely poor prognosis and a high potential for malignancy with hematogenous and lymph node metastases. A 90-year-old man who had carcinoma ofthe sigmoid colon 2 years ago was found to have rectal NEC based on endoscopy findings. He underwent the Hartmann operation. Histological and immunohistochemical analyses showed NEC. Four months after the surgery, he developed local recurrence with lymph node metastasis. He was not administered chemotherapy because ofhis old age. Although the patient needed strict outpatient care, he remained symptom-free 4 months after the Hartmann operation.