Understanding the mechanisms involved in intracellular movement and localization of proteins is a central issue in cell biology. This volume is concerned with the events involved in the transport of membrane proteins, and the contents of vesicular compartments, to their ultimate destinations. In several chapters, particular attention is given to studies with viruses that are assembled by budding at specific membrane sites within the cell or at the cell surface; studies with such viral systems have provided significant insights into membrane biogenesis.