Alterations in mammalian is a frequent result of viral infection. Productive as well as nonproductive infection by enveloped viruses often results in modification of host cell membranes. In addition viral mediated cell transformation is accompanied by changes in the cell surface. This project is designed to explore the synthesis of viral membrane proteins and the steps involved in their incorporation into host membranes and viral membranes. These studies will make use of Vesicular Stomatitis Virus and Newcastle Disease Virus. Specifically this project includes: 1. An analysis of the steps involved in the insertion of viral membrane proteins into host plasma membranes. 2. Identification of the interactions between viral proteins necessary for virion assembly at the plasma membrane. 3. Characterization of the defects of temperature sensitive mutants defective in assembly.