The aim of this study was to establish cell lines of adenocarcinomas of the gastro-esophageal junction(GEJ), which grow in vivo and in vitro. Primary esophageal and gastric cardia adenocarcinomas and corresponding lymph node metastases were xenografted subcutaneously to immunodeficient nude mice. In addition, tumor tissue was also used for in vitro culture. Xenografting of 70 primary adenocarcinomas and 17 metastases resulted in the initial growth of 22 and 6 tumors, respectively (total 32%). Upon retransplantation, six long-term xenografts [esophageal adenocarcinoma (OAC)P33X, OACP47X, OACP56X, OACP58X, OACP67X, OACP76X] from primary tumors and three (OACM2.1X, OACM30X, OACM53X) from metastases were obtained. In vitro culture attempts of 34 primary tumors and nine metastases resulted in the establishment of three (7%) permanent in vitro growing cell lines. From one patient, a cell line from the primary tumor (OACP4 C) and from a lymph node metastasis (OACM4.1 C) was established. The third cell line (OACM5.1 C) was also derived from a lymph node metastasis. The in vivo and in vitro cell lines were characterized using immunocytochemistry and microsatellite analysis to verify their epithelial and human tumor origin, respectively.