In this paper we deal with the effect of silicon interstitials on metal precipitates. We show that excess silicon interstitials which are injected by common gettering treatments cause most metal precipitates to shrink but a few to grow. Data from the literature confirms that the precipitates which grow by the absorption of silicon interstitials (primarily FeSi2and NiSi2) are found exclusively in regions that act as net injectors of silicon interstitials. Other precipitates shrink in the presence of excess silicon interstitials and are easily gettered. This explains why silicon interstitial injection is essential for effective gettering.