The potential for liver metastasis in addition to the transplantability and doubling time of alpha-fetoprotein(AFP)-producing and non-AFP-producing human gastric carcinomas were studied in nude mice. The potential for liver metastasis was analyzed histopathologically from intrasplenic injections of tumor cell suspensions prepared from subcutaneous tumors. Tumor fragments prepared aseptically from 15 AFP-producing and 140 non-AFP-producing gastric cancers were subcutaneously transplanted into nude mice with transplantability rates of 80% (12/15 cases) and 50% (70/140 cases), respectively. The mean tumor doubling times in the first generation were 10.6 days for AFP-producing and 13.2 days for non-AFP-producing gastric carcinomas. Serially transplantable tumor lines in nude mice were established from six AFP-producing and 10 non-AFP-producing carcinomas. When tumor cell suspensions prepared from the subcutaneous tumors were injected into spleens, all six AFP-producing carcinomas (two poorly differentiated and four tubular adenocarcinomas) but only four out of the 10 non-AFP-producing carcinomas (two poorly differentiated adenocarcinomas, one mucinous carcinoma and one papillary adenocarcinoma) demonstrated a potential for liver metastasis. The results indicate AFP-producing gastric carcinomas to possess a higher potential for liver metastasis than do non-AFP-producing carcinomas, a distinguishing feature which thus reflects a poor prognosis.