Peritoneal mesothelioma is rare, and the sarcomatoid variant is more infrequent, with <30 cases reported to date in the literature. Several case series have described the morphologic features of sarcomatoid peritoneal mesothelioma (SPe); however, the clinicopathologic features are not well characterized. To our knowledge, this is the first large series reporting the clinicopathologic features of SPe. We reviewed our database of 3106 malignant mesothelioma cases. Of 248 peritoneal mesotheliomas, 15 (4%) were sarcomatoid variant (0.5% of all mesotheliomas). Only cases with 100% sarcomatoid morphology diagnosed by open surgical biopsy and/or autopsy were included. Thus, 4 cases were excluded leaving 11 cases of SPe. Two additional cases of SPe previously published by 1 of the authors (V.L.R.), not included in the database, are added yielding 13 cases total. The median age at diagnosis was 66 years (range=48 to 85 y), and there was a male predominance (M:F=3.25:1). Survival from date of diagnosis to date of death was 5 months (range=0 to 12 mo). The most common presenting symptom was abdominal pain, and 3 of 4 women were suspected to have cholecystitis/cholelithiasis. All cases stained positive for cytokeratins, and 2 contained heterologous elements. Seven cases had objective markers of asbestos exposure, and 2 additional cases had occupations strongly associated with mesothelioma. Two cases with alleged household contact exposures could not be confirmed to be asbestos related by lung fiber analysis. SPe is a rare variant of mesothelioma attributed to asbestos exposure in 69% of our cases.