Data collected by population-based cancer registries in Iowa and metropolitan Atlanta were evaluated to determine prognostic factors for gastrointestinal (n = 270) and bronchopulmonary (n = 151) carcinoids. The predictors considered in univariate and multivariate analyses were: age, sex, race, marital status, anatomic subsite, stage, occurrence of other malignancies, and surgery. For surgically treated gastrointestinal tumors, the cumulative percentages of survivors at five years were: appendix, 85.6%; small intestine, 66.0%; and large intestine, 37.7%. The likelihood of death from gastrointestinal carcinoids was found to be related independently to increasing age (P = 0.001), advanced stage (P less than 0.0001), location within the large intestine (P less than 0.0001), and occurrence of another malignancy (P = 0.02). The overall five-year survival rate for bronchopulmonary carcinoids was 87.6%, and lack of surgical treatment (P less than 0.0001) and advanced stage (P = 0.006) were associated independently with unfavorable prognosis.