Further study of human transitional cell cancer would be facilitated by propagation and positive identification of benign and malignant urothelial cells in vitro. Recent experience indicates that this is now feasible. Explant and dispersion cultures of human malignant (primary and metastatic) and non-malignant transitional tissue cells obtained at surgery will be established to identify the optimal conditions for cell growth and propagation. Microdissection techniques will be used to insure that the starting material has little adherent fibromuscular tissue. Various dispersion techniques and support media will be examined. The cell populations established will be monitored visually to insure that the morphology of the recovered cells is not that of non-malignant supporting stroma. Colony characteristics of the recovered cells will be examined both in soft agar and on chick chorio- allantoic membrane. As mammalian transitional epithelium is characterized by an asymmetric unit membrane with specialized subsurface discoid vesicles, ultrastructure studies will be conducted on these cultures to determine the persistence of this specific morphologic marker. Cloning and karotyping will be conducted as appropriate. The primary effort will be (a) to define the optimum in vitro environment for the initiation, maintainance and propagation of malignant and non- malignant urothelium, (b) to develop methodology for the positive identification of the cultured cell as urothelial in origin, and (c) to provide malignant and non-malignant urothelium and their support media for the comparative morphologic, biochemical and immunologic studies of non-malignant and malignant transitional epithelial cells.