Mullerian-type mucinous tumors (MMTs) of the ovary are characterized by a papillary architecture similar to that of serous tumors and a content of endocervical-like mucinous epithelium. The latter may be admixed with other mullerian-type epithelia, including those of serous, endometrioid, and squamous types, and indifferent eosinophilic epithelial cells. We analyzed 17 MMTs, including 12 borderline tumors, 2 intraepithelial carcinomas, 2 microinvasive carcinomas, and 1 invasive carcinoma. Fourteen of 16 tumors (88%) with available staging were stage I; the remaining two cases (both borderline) were stage IIa and IIIc. Endometriosis was identified in eight cases (47%). Only two patients (12%) had bilateral tumors, a frequency of bilaterality lower than in previous studies. Five patients (31%) had conservative treatment consisting of a cystectomy or unilateral salpingo-oophorectomy. All patients had a favorable outcome, with no recurrences or disease-related deaths, regardless of the presence of high mitotic index, intraepithelial carcinoma, microinvasion, bilaterality, conservative treatment, or advanced stage. This indolent behavior of MMTs is similar to that previously reported, but additional cases of invasive carcinomas in this category are needed to better define their outcome.