Cover photograph (Copyright © 1999, American Society for Microbiology. All rights reserved.): Three-dimensional structure of cytoplasmic polyhedrosis virus, a single-shelled member of the Reoviridae, was determined to 17-Å resolution from electron cryomicroscopy images. The full virus (top), which is color-coded according to particle radius, has a T=1 icosahedral capsid shell decorated with 12 characteristic pairs of concentric spikes at its vertices. Structural comparisons of the full and empty capsids have revealed ordered double-stranded RNA inside the full capsid (lower left, yellow and red) and its interactions with the transcriptional enzyme complexes (lower right). (See related article on page 1624.)