(Revised Abstract) DESCRIPTION (provided by applicant): The analysis of macromolecular structures by X-ray crystallography provides data critical for an understanding of the beneficial and adverse functions of biological macromolecules and assemblies associated with cancer, which is the focus of research in the Cancer Center's Structural Biology Program. Current studies embrace a wide range of crystallographic research pertaining to basic processes associated with cancer as well as to its prevention and treatment. The Macromolecular Crystallography Resource supports a strong program of cancer-related crystallographic research and hopes to stimulate the development of new research by assisting nonspecialists and promoting cross-program collaborations. The Resource provides advanced facilities for macromolecular crystallography as well as experienced technical support to maintain these facilities in superb working condition for direct use by Cancer Center researchers. The essential facilities include laboratories equipped for X-ray diffraction experiments and for the crystallization of macromolecules. Key diffraction instruments include two 12kW rotating anode X-ray generators and three imaging plate diffractometers equipped with focusing mirror or multilayer optics and cryogenic crystal cooling devices. Equally critical to the success of the Resource is the involvement of very experienced support personnel who coordinate hardware and software maintenance and development. The Resource is heavily and almost exclusively used by Cancer Center members.