The aim of the research was to assess possible histopathological differences between BRCA1- and BRCA2-associated malignant intraperitoneal (ovarian/fallopian tube/peritoneal) tumors and their sporadic counterparts. Dutch families harboring pathogenic BRCA1 or BRCA2 mutations were selected. Included were patients who had had malignant primary ovarian, fallopian tube or peritoneal tumors. Histopathological data was compared with data obtained from the Dutch cancer registry between 1989 and 1993 (reference group). A total of 63 with primary intraperitoneal malignant tumors were identified in 41 families. Non-epithelial malignant tumors were not observed in the study group versus 6% (n = 404) in the reference group (n = 6789, P = 0.04). These tumors were excluded from further analysis, as were ovarian adenocarcinomas not otherwise specified, since these were detected in 22% of the study group, and in 19% of the reference group (P = 0.76). Serous carcinomas were detected in 94% (47/50) of the women in the study group in contrast to 62% (3145/5088) of the reference group (P < 0.01). In the study group, mucinous and endometrioid ovarian adenocarcinomas and serous ovarian borderline tumors each comprised 2.0% of the tumors. Clear cell ovarian carcinomas were not detected. In contrast, these percentages were 16% (P < 0.01), 10% (P = 0.07), 7% (P = 0.16) and 5% (P = 0.12), respectively, in the reference group. In the study group, 6.0% of the carcinomas arose in the fallopian tube versus 1.9% in the reference group (P = 0.03). Four percent of the study group developed primary serous peritoneal carcinomas, versus six percent in the reference group (P = 0.57). Serous carcinoma is the predominant type of intraperitoneal malignancy occurring in women harboring BRCA1 or BRCA2 mutations. Non-epithelial cancer does not seem to be part of the tumor spectrum of BRCA mutation carriers. This suggests, therefore, that serous tumors may be the only subtype related to a BRCA1 or BRCA2 mutation. Furthermore, fallopian tube carcinoma occurred more often in BRCA mutation carriers than in the reference population.