A rigid contact scope is a recent development of optical instrument which allows observations of the superficial layers of the mucosai epithelium in gynecology and otorhinolaryngology. To assess the evaluation of 25 patients with advanced gastric cancer, whose lesions had been diagnosed to be more than T3 or suspected to have peritoneal deeding, we performed pre operative laparoscope with rigid contact scope. After inspecting a usual laparoscopic observation of the abdominal cavity, serosal exporsure and peritoneal seeding were confirmed. All the patients who had serosal exporsure and cancer cells showed an irregularity of cell distribution with the extent of heterogeneity of the cells with nuclei size and shape. Five patients had peritoneal seeding, and the findings with rigid contact scope showed a similar view to cancer cells which were observed in serosal exposure. The result suggests that this new endoscopic technique enabled a new diagnostic approach in advanced gastric cancer.