InterViewer, RGD’s new Cytoscape-based protein-protein interactions viewer, facilitates a detailed visualization of interactions between proteins. Access InterViewer via the "Analysis & Visualization" (formerly ‘Genome Tools’) tab on the RGD front page. On the "InterViewer – Protein Interactions – Query Form" page, select the species (or use the default "all") and enter a list of UniProt IDs, RGD IDs or gene symbols. On the display page, binary interaction data from IMEX are displayed as nodes and edges, which can be zoomed in or out using controls on the left (1). Clicking on a protein node after zooming in (2) provides links to UniProtKB and to RGD gene report pages. Detailed information about the protein appears in the upper right. Select the display format on the right. Below that, a legend details the color-coded interaction types and protein species (3). The table beneath the display (4) lists downloadable characteristics of each pair of interactors. Also available here are tabs for a node list and node/edge statistics. Click and drag the blue panel in the bird’s-eye view in the lower right (5) to move the display, or click and drag the display itself. Click an edge to display information about that interaction. Copy and paste the list of test genes below into the Query Form page to try out InterViewer.