We have developed new software (OLEX) for the visualization and analysis of extended crystal structures. This software has a Windows-compatible mouse-driven graphical interface which gives full control over all structural elements. OLEX provides the user with tools to construct topological networks, visualize interpenetrating or overlapping fragments, and analyse networks constructed fully or partially by exploiting short interactions. It is also easy to generate conventional ellipsoid, ball-and-stick or packing plots.