We report on the establishment of a new scirrhous gastric cancer cell line with microsatellite instability (MSI), designated OCUM-7. This cell line was derived from a primary scirrhous gastric carcinoma. The cells were floating and round shape in culture. Histologic findings of xenografted tumor obtained from OCUM-7 cells showed a poorly differentiated adenocarcinoma with medullary growth. DNA histograms of OCUM-7 cells showed an aneuploid pattern. MSI status of OCUM-7 was analyzed using 8 microsatellite markers. Five of 8 microsatellite loci showed a novel band shift, which demonstrated that OCUM-7 cells were MSI-high. MSI-positive cell lines established from a primary scirrhous gastric carcinoma have not been reported, while several reports of the establishment of a scirrhous gastric cancer cell line are available. OCUM-7 might be beneficial for analyzing the mechanisms of MSI in scirrhous gastric carcinoma.