A human gastric cancer cell line, designated GCIY, was established from ascites of a patient with scirrhus type gastric cancer. Doubling time of this cell line was 55 hours. The karyotype indicated that these cells were human cells and the chromosome number varied widely, the mode being 57. GCIY cells were of moderate size and showed monolayer arrangement. They had a large nucleus and a clear nucleolus. Papanicolaou staining showed that they had the characteristics of adenomatous epithelia. They could be subcutaneously transplanted into nude mice, and they histologically resembled the original tumor. They were immunohistochemically recognized by anti-CA19-9 antibody and weakly by anti-CA125, CEA and alpha FP antibodies. Cultured medium also contained CA19-9, CA125, CEA and alpha FP.