Carcinoid of the appendix occurred in 92 of 400,000 surgical pathology specimens covering 70 years, and followed previously reported incidences by age, sex, symptoms, size, localization and histology. Invasion of the mesoappendix occurred in 13 cases, and in two of these, a reoperative ileocolectomy demonstrated regional node metastases. No distant metastases or fatalities appeared. Tumor size correlated with mesoappendiceal invasion. Carcinoid invasion of the mesoappendix may provide a valuable marker for more distant tumor spread, and justify an aggressive surgical approach in selected patients.