The self-interstitial defect is commonly regarded as important in regulating diffusion in silicon. A review of the literature reveals that the scientific bases for invoking the self-interstitial defect are weak, while an alternate defect, the vacancy cluster, has been largely ignored. One argument which has been used to establish dominance of the self-interstitial defect over vacancies is based upon attempts to model gold diffusion. Possible behavior of vacancies are considered, and the past analysis is found to be inconclusive. Another argument which has been presented as evidence for presence of silicon self-interstitials is based on observations of type "A" swirl defects. These defects are amenable to interpretation in terms of solidification theory, without need to invoke the interstitial point defect. Two experiments were designed to demonstrate influence of heat treatments upon gold diffusion in electronic grade silicon crystal when the heat treatment was performed prior to gold deposition. Results are interpreted in terms of Ostwald ripening of vacancy clusters retained in the crystal from high temperature processing. / Graduation date: 1996