Independently and not as an agent of the Government, the Contractor shall exert its best efforts to perform studies of carcinogenesis in organ culture of trachea and bronchi. In performance of this project the contractor will develop a reproducible method of growing large numbers of uniform cultures of tracheal epithelium and associated connective tissues, carefully defining conditions of culture and delineating the biologic characteristics of the tissues when in culture. Cultures will be derived from inbred strains of rats which can serve as both sources of implants and recipients in biological tests of malignant transformation by carciogens. Techniques fo implatation with circumvention of immune mechanisms, if necessary, will be perfected. Known pulmonary carciogens will be selected for transformation and protocols for exposure to the carcinogens developed.