The proposed conference will be the fifth of a new series of Gordon Conferences on Three-dimensional Electron Microscopy of Macromolecules. Electron microscopy has developed rapidly in recent years as a powerful tool for structure research at the molecular level. Important technical breakthroughs have been made which enable three-dimensional structure to be determined with increasing accuracy, and which have opened the way to a study of structure essentially under controlled physiological conditions. As a result, there are exciting new opportunities for understanding biological mechanisms and principles of molecular design. The unique position of this series of conferences derives from the fact that they help foster an integrated view of biological complexity, by bringing together scientists working on different levels of the structural hierarchy. The focus of this meeting will be to coalesce ideas concerning the preparation and visualization of biological specimens that span an extremely wide size range, extending from the near-atomic all the way to the cellular and beyond. Important recent structural findings, relating especially to membrane proteins, viruses, cell organelles, and cytoskeletal structures will be emphasized in addition to practical aspects of instrumentation and computational methods of three-dimensional reconstruction. This conference will help catalyze the further development of this field by bringing together many of the key investigators and allowing them to discuss their latest studies and perhaps even incomplete studies in a unique and informal setting. Speakers are being chosen on the basis of the importance of their recent research contributions and the potential of their particular approach in future structure research. Topics to be covered include: hybrid technology (electrons and x-rays working together), advances in crystallization, computation, and instrumentation, a rebirth of non-cryogenic preparation techniques, site-specific labelling of macromolecules, methods of three-dimensional reconstruction, progress on image formation, acquisition, and display, and recent structural results obtained for a variety of macromolecular and cellular assemblies and viruses.