We report here that a mouse mutant (C.B-17 scid) which lacks functional B- and T-lymphocytes can be used to propagate a human lung tumor. The heterotransplanted tumor cells generated palpable s.c. tumors by 18 days in 100% of the mice inoculated s.c. with greater than 4 X 10(6) cells. All tumors grew progressively with no sign of regression. A portion of the scid mice given injections i.v. of the human lung tumor cells developed multiple tumor nodules in the lung by 15 weeks after the inoculation of tumor cells. The tumor nodules were shown by karyotype analysis to be human cells, and the histopathology of the tumor nodules revealed a pattern of growth that was consistent with that of the original tumor. The human lung tumor used in the study expresses an Mr 160,000 cell surface glycoprotein that has been shown to occur on a large proportion of human lung tumors and tumor cell lines. A monoclonal antibody specific for Mr 160,000 glycoprotein was used to demonstrate that this tumor-associated antigen is stably expressed by the s.c. tumors and the lung tumor nodules in the scid mice. The mutant mice with this severe combined immunodeficiency represent a new and viable model for propagating human tumors and for evaluating the efficacy of novel drug delivery protocols in the treatment of human cancer.