To study surface and other changes in transformed cells and the molecular mechanisms responsible for antigenic changes and/or the transformation to malignancy, either spontaneously or as induced by SV40 virus. To gain a better insight into the biological activity and function of new proteins and antigens which appear after transformation. To develop better methods to isolate and purify cell surface membranes, and antigenic components such as SV40 virus specific T antigens, surface antigens and tumor specific transplantation antigens; and to study their interrelationships.