During 2004 to 2011, 81, 420, and 166 patients with colorectal cancer (CRC), epithelial appendiceal neoplasm (APN), and gastric cancer (GC) with PC were treated with cytoreductive surgery (CRS) plus perioperative chemotherapy. CRS was performed by peritonectomy techniques using an aqua dissection. Results. Complete cytoreduction was done in 62/81 (76.5%), 228/420 (54.3%), and 101/166 (60.8%) of patients with CRC, APN, and GC. The main reasons of incomplete resections were involvement of all peritoneal regions and diffuse involvement of small bowel. The incidence (64%, 302/470) of CC-0 resection after introduction of an aqua dissection was significantly higher than before (42%, 82/197). A total of 41 (6.1%) patients died postoperatively. Major complication (grade 3-4 complications) occurred in 126 patients (18.9%). A reoperation was necessary in 36 patients (5.4%). By the multivariate analysis, PCI scores capable of serving as thresholds for favorable versus poor prognosis in each group and CC scores demonstrated as the independent prognostic factors. Conclusions. Peritonectomy using an aqua dissection improves the incidence of complete cytoreduction, and improves the survival of patients with PC. Patients with PCI larger than the threshold values should be treated with chemotherapy to improve the incidences of complete cytoreduction.