A very select group of dialkyl-N-nitrosamines are to be synthesized and selectively labeled with C-14. Using the labeled compounds in vivo and in vitro (isolated liver perfusion and microsomes), metabolic studies will be performed and the metabolites will be identified. Also, followng administration of the labeled compounds to animals, the extent and nature of bound radioactivity to purified nucleic acids will be determined. As a means of testing the current hypotheses on N-nitrosamine mode of carcinogenic action, model N-nitrosamines will be synthesized and tested in three species of animals.