Oxygen in silicon has been an important scientific and technological subject for over 30 years. It derives its technological importance from the fact that silicon crystals pulled from silica crucibles have been the standard substrates for fabrication of integrated circuits. The scientific interest originates both from support of this technology and the wide variety of phenomena that occur when cooled Czochralski (CZ) Si crystals become supersaturated with oxygen. Furthermore, the semiconducting nature of Si permits the use of very sensitive electrical and optical probes to complement the structural and chemical characterization of these varied solid state phenomena.