The aims of this study were to calculate the true incidence of colonic carcinoids in Connecticut from 1976 to 1986 and to determine the outcome of patients with these lesions. Fifty-four patients with carcinoids of the colon were identified (23 male and 31 female patients). Their average age was 64.1 +/- 2.1 years, with a range of 12 to 83 years. The age-adjusted incidence was 0.31 cases/100,000 population/year. Forty-eight percent of the carcinoids were located in the cecum; 16%, ascending colon; 6%, transverse colon; 11%, descending colon; 13%, sigmoid colon; and 6%, not assigned. Follow-up information was available in all cases. The crude 2-year survival rate was 63%, whereas the 5-year survival rate was 37%. Only one of six (16.6%) lesions that were 2 cm or smaller metastasized, whereas 23 of 31 lesions larger than 2 cm metastasized (74%). Six patients have survived an average of 43.5 months after local excision of their carcinoids. Fourteen patients died of their carcinoids. Metachronous gastrointestinal malignant neoplasms developed in six patients. These results suggest that, when found at an early stage, carcinoids of the colon (2 cm or smaller) can be treated by local excision. The vast majority of colonic carcinoids, however, are discovered at an advanced stage and should be treated aggressively with standard colonic resection. In addition, surveillance of the entire gastrointestinal tract should be initiated in these patients because of a high rate of other gastrointestinal malignant neoplasms.