The usefulness of an in vitro human tumor culture system using a specialized collagen gel matrix derived from pig skin was retrospectively evaluated as a chemosensitivity test for human gastric carcinomas. Seven xenograft tumors derived from human gastric cancers were examined by this system (CGM assay) and compared with the data obtained by a nude mice assay (NM assay) and a succinic dehydrogenase inhibition test (SDI test). Xenograft tumors had three-dimensional growth on the collagen gel matrix like that in vivo. There was increasing cell kill with rising cytotoxic drug concentration. When drug sensitivity was evaluated as effective based on an inhibition rate of 40% or more in the CGM assay, drug sensitivity as measured by the CGM assay corresponded with that measured by the NM assay for all xenograft tumors but not the SDI test. This system could be applied for chemosensitivity test of scirrhous gastric carcinomas. It was suggested that the CGM assay may be more like an in vivo like chemosensitivity test and clinically useful testing for the patients with gastric cancer, including scirrhous one.