Carcinoid tumors are the most common neoplasms of the appendix. Histologically they have been categorized as classical, tubular, or goblet cell types. Goblet cell carcinoid has been regarded as a distinctive tumor type, not related to classic carcinoids, and to our knowledge combinations of these 2 tumor types have not been described in detail. In this report, we describe 5 cases of combined classical carcinoid and goblet cell carcinoid (GCC) tumors of the appendix. Four men and 1 woman, (mean age 53.4 y) presented with acute appendicitis (4 cases), whereas 1 presented with a pelvic mass owing to widespread pelvic disseminated disease. The tumors (0.6 to 6.0 cm) were located in the mid-portion and the tip of the appendix. Four patients were treated with right hemicolectomies (the patient with disseminated pelvic and ovarian metastases also had a pelvic exenteration), and 1 was treated with an appendectomy only. Four patients are alive and asymptomatic, whereas the patient with disseminated pelvic disease died 6 months after surgery. All 5 appendiceal tumors had microscopic features of both classical carcinoid and GCC, either intimately admixed or separate but closely apposed. The extent of the 2 components varied, with classical carcinoid representing 60% to 90% of the tumor. Both components stained for the general neuroendocrine markers, however, staining in the classic component was greater. The Mib-1 proliferation index varied from 1-15%, again with higher Mib-1 indices seen in the GCC component of all 5 cases. The pelvic soft tissue and ovarian metastases in case 4 consisted predominantly of a signet ring cell carcinoma with a minor component of goblet cells and was interpreted as an adenocarcinoma ex-GCC. In view of the fact that these combined carcinoid tumors appear to behave more as goblet cell carcinoids, detailed microscopic examination of classical carcinoid tumors of the appendix is suggested and larger series with longer follow-up is required to ascertain the true biologic potential of this unique form of combined carcinoid tumor of the appendix. The occurrence of both carcinoid types in the same appendices suggests a closer histogenetic relationship than previously believed, although the possibility that the 2 components represent separate, independent primaries ("collision tumors'') can also be considered.