Background: Primary malignant tumors of appendix are uncommon and usually found during the pathological examination of surgical pieces of appendectomies. Aim: To report the clinical and pathological features of appendiceal malignant tumors. Material and Methods: Review of medical and pathological reports of patients subjected to an appendectomy between 1998 and 2006 in two regional hospitals. Results: Fifteen appendiceal malignant tumors in 2,687 pathological studies were detected (0.55% of all studies) in one hospital. In the other 10 tumors were detected in 4,939 studies (0.2%). Nine bearers of tumors were male. In each hospital 93 and 80% of patients had an acute appendicitis, respectively. The pathology report informed a neuroendocrine tumor in 87 and 70% of patients of each hospital, respectively, followed by non-Hodgkin lymphoma and adenocarcinoma. In nine patients a staging study was performed. Four patients died during follow up, one of them due to tumor disseminations. Conclusions: Although appendiceal tumors appear in only 0.3% of all appendectomies, the pathological study of the excised appendix is fundamental for the diagnosis.