The technique of X-ray crystallography is a powerful tool for the determination of the molecular structure of compounds as diverse as small polypeptides and complex metal clusters. When combined with the latest computer software, the technique is becoming remarkably easy to put into practice. The acquisition of X-ray crystallographic instrumentation markedly improves the ability of chemists to carry out frontier research. This award from the Chemistry Shared Instrumentation Program will help the Department of Chemistry at the University of Houston to acquire an X-ray diffractometer. The areas of chemical research that will be enhanced by the acquisition are as follows: 1) Structure reactivity relationships for dirhodium complexes 2) Structural studies of metal-metal and metal-carbon metalloporphyrins 3) Charge transfer salts 4) Mechanistic and synthetic studies on biologically relevant molecules 5) Natural products structure 6) Novel ligand systems.