Appendiceal carcinomas are classified into three distinct histopathological disease entities: disseminated peritoneal adenomucinosis (DPAM), peritoneal mucinous carcinomatosis (PMCA), or peritoneal mucinous carcinomatosis with intermediate or discorant features (PMCA I/D). The treatment of appendiceal tumors should be based on accurate histopathological classification, per previously reported case series. The objective of this study was to evaluate the clinicopathologic presentation and outcome of patients with appendiceal tumors treated at our institution over a 15-year period. We identified patients with appendiceal tumors diagnosed or treated at our institution from January 1989 through May 2004. Chart review for age, gender, signs and symptoms at diagnosis, and treatment was performed. Review of the pathologic specimens was performed and tumors were classified as DPAM, PMCA I/D, or PMCA. Forty patients were identified (median age 52.5 years; males 38%). The number of patients with DPAM, PMCA I/D, and PMCA was 15 (38%), 6 (15%), and 18 (46%), respectively. Peritoneal involvement was seen in 11 (73%) of patients with DPAM, 5 (83%) of PMCA I/D, and 11 (61%) of PMCA. The median survival for patients with DPAM, PMCA I/D, and PMCA was 7.7 years (90% CI: 2.9--upper limit not estimable), 1.2 years (90% CI: 0.9-1.6), and 0.7 years (90% CI: 0.4-1.5), respectively. The difference in survival across the three groups was statistically significant. Three distinct histopathological disease entities exist in appendiceal tumors. The prognosis and management of these tumors should be based on the extent of disease and pathologic diagnosis.