Cell surface changes are widely suspected to play an important role in loss of cell density-dependent growth control following viral transformation. Our research objectives are determining whether changes in cell surface acid mucopolysaccharides, intercellular cyclic AMP levels and the microtubule/microfilament system interact to produce the cell surface changes characteristic of virus transformed cells. In addition, we are evaluating whether the enhanced levels of specific proteolytic enzymes in virus transformed cells are the cause of any of their altered growth or cell surface properties. We are employing temperature sensitive viral and cellular mutants, as well as density inhibited revertant cell lines to attempt to identify those viral and cellular functions whose interaction leads to the cell surface changes and unrestrained growth of virus-transformed cells.