Summary Introduction and aim Neuroendocrine carcinomas (NEC) of the large intestine are rare and aggressive neoplasms. This study was designed to review the experience at a single institution and analyze the outcomes to improve our understanding of these tumors. Methods The patients with NEC (high-grade neuroendocrine tumor) of the colon, rectum, and anal canal were identified from June 1993 to April 2011. Clinical features studied were patient demographics, presenting symptoms, tumor location, tumor stage, treatment status and length of follow-up. Results Twenty-five patients were identified. Stages of the diseases were I (n=5), II (n=1), III (n=10) and IV (n=9). Locations of the tumors were: colon (36%); rectum (28%) and anal canal (36%). Rectal bleeding (36%) and pain (32%) were the most common symptoms but 16% of patients were asymptomatic. Among the patients with local or locally advanced disease, only five patients had surgery alone. The remainder of the patients underwent chemotherapy with/without radiation. Mean follow-up was 33.7±8.4months after diagnosis. NEC of the large bowel and anal canal has very distinctive pathologic features and a very poor prognosis. More than one third of the patients with NEC had metastatic disease at the time of diagnosis. When these tumors are in an advanced stage none of the treatment modalities impact on survival. Conclusion The present study showed the poor prognosis of these rare tumors.