Pseudomyxoma peritonei (PMP) is a rare entity that is characterised by abundant intraperitoneal mucinous and gelatinous material associated with an intraperitoneal adenocarcinoma. We report the case of a patient who presented with PMP associated with a ruptured well-differentiated mucinous adenocarcinoma of the ovary and an infiltrating moderately-differentiated mucinous adenocarcinoma of the sigmoid. Diagnosis was made by ultrasonography and CT. Due to the presence of 2 mucinous tumors with different histological grade the most likely pathogenesis was that of multifocal metaplasia. The ovarian and colonic mucinous tumors were independent primary neoplasms and PMP probably was the result of rupture of one of these tumors with peritoneal seeding of viable mucus secreting tumor cells. Aggressive surgical debulking in addition to left hemicolectomy and radical hysterectomy were performed.