Objective-To describe the technique of diaphragmatic peritonectomy (DP) for ovarian cancer cytoreduction and to assess associated morbidity.Methods-Retrospective review yielded 56 patients who underwent DP as part of a cytoreductive procedure for primary or recurrent ovarian cancer between 1988 and 2004. Patients who underwent diaphragmatic resection, removal of diaphragmatic implants with CUSA, cautery, curette, or finger fracture, and patients with pseudomyxoma were excluded from analysis.Results-DP was performed as a component of primary or secondary cytoreduction in 37 (66%) and 19 (34%) patients, respectively. Extended procedures including bowel resection, hepatic resection, splenectomy, or radical hysterectomy were performed with DP in 47 patients (82%). Resection of all disease > 1 cm was achieved in 95% (microscopic residuum in 43%). For those undergoing primary cytoreduction, median survival was 59 months and 5-year survival was 49% with median follow-up of 34 months. When performed for recurrent ovarian carcinoma, 5-year survival was 16% and median survival was 23 months. No intra-operative complications could be specifically attributed to DP. Post-operative complications included a 30% rate of pleural effusion which was associated with entry into the pleural space during DP (p<0.0001); thoracentesis was required in 12.5%.Conclusions-Diaphragmatic metastases are a common obstacle to optimal cytoreduction for patients with ovarian cancer. When necessary, utilizing DP in concert with other extended procedures to obtain maximal cytoreduction is associated with excellent survival. It should be recognized that DP is associated with an increased incidence of post-operative pleural effusion, particularly when the pleural space is entered.