The process of adhesion to endothelial cells is an important step in the progression to metastatic disease. The use of human neoplastic cell lines (now increasingly used in the study of the mechanisms of metastasis) in studying interactions with normal endothelial cells is therefore pertinent. In this report, the enhanced ability of a metastatic variant, MV522, of a human lung carcinoma cell line to adhere to endothelial cell monolayers is demonstrated. The ability to spontaneously metastasize from subcutaneous sites in athymic mice, of in vitro selected endothelial adhesive subpopulations of MV522 is also shown.