Peritoneal metastases originating from colorectal cancer (CRPM) and gastric cancer (GCPT) occur frequently (metachronous in 15 to 40% of patients) and are most often diagnosed at an advanced stage because symptoms are sparse at the initial stages of disease. Abdominal-pelvic computed tomography with or without arterial and portal phase evaluation is essential for the diagnosis of recurrence or peritoneal involvement. However, exploration of the peritoneal cavity by laparoscopy can confirm the diagnosis and provide histological evidence. It is crucial to distinguish between palliative and potentially curative treatments; the latter based on complete resection of disease, the feasibility of which depends on technical, oncological and physiological criteria. The treatment of CRPM and GCPM is based on systemic chemotherapy (associated with or without targeted therapy) potentially combined with complete cytoreductive surgery (CRS) in selected patients and performed in expert centers. The survival benefit of CRS in patients with CRPM has been validated with a median survival of 41 months (PRODIGE 7). Regarding the addition of hyperthermic intraperitoneal chemotherapy (HIPEC) to CRS, mitomycin C is the preferred drug used and a phase-3 randomized trial comparing CRS plus HIPEC to mitomycin C versus CRS alone, is underway in Spain. Regarding GCPM, survival results after CRS, after CRS plus HIPEC, or after systemic chemotherapy alone, remain disappointing. The goal of CONVERGENCE, an international trial (starting soon in France), will be to evaluate the benefit of CRS in these patients. The prognosis of colorectal and gastric peritoneal disease (PD) has improved substantially in recent decades, thanks to better knowledge of these entities, managed surgically and oncologically in expert reference centers. The potential benefits of HIPEC in combination with CRS are under evaluation in randomized trials.