Given that JSRV Env is capable of inducing tumors in both sheep and mice, and due to the controversy surrounding the role of JSRV in human lung cancer, we decided to examine multiple types of human lung tumor samples for the presence of JSRV Env by immunohistochemical staining of lung cancer tissue arrays with an Env-specific monoclonal antibody and by PCR amplification with env- and gag-specific primers. Here, ERVW-1 is linked to lung carcinoma.