The signet-ring cell adenocarcinoma cell line (HSKT-C) and the fibroblast cell strain (HSKT-F) were established from a Krukenberg tumor. The HSKT-C cells are small, roundish or spindle-like in shape and form monolayer sheets of epithelial pavement cells and produce carcinoembryonic proteins such as carbohydrate antigen 19-9 (CA 19-9), carcinoembryonic antigen (CEA), tissue polypeptide antigen (TPA), etc. They show a stable proliferation after successful passages of 45 times within 13 months. The chromosome number varied widely and showed aneuploidy. The HSKT-C cells were transplanted to hamster cheek pouches and produced a tumor (signet-ring cell adenocarcinoma). On the other hand, HSKT-F cells are fibroblast-like. Their chromosome number is 46, and no karyological abnormality was observed. They could not be transplanted in the nude mouse or the hamster and did not produce carcinoembryonic proteins. It should be noted that they produce estrogens (estrone and 17 beta-estradiol). Sarcomatous morphological change of the stromal cells in Krukenberg tumor is considered to be a reactive change against invasion of the signet-ring cell adenocarcinoma into stromal tissues.