The depth variation of oxygen and carbon precipitation in multicrystalline sheet silicon has been examined by infrared microspectroscopy, electron-beam induced current (EBIC), and preferential defect etching. Experimental results on the depth profiles of interstitial oxygen (O-i), substitutional carbon (C-s), and oxygen precipitates, plus numerical analyses of vacancy-interstitial distribution indicate that oxygen precipitation is controlled by the initial O-i concentration and quenched-in vacancies. In addition, it is found that the C-s depth profile in the annealed samples mimics the O-i profile. Examination of the precipitate density and the C-s reduction rate allows us to show that formation of interstitial carbon by capturing self-interstitials generated during oxygen precipitation is a necessary step in explaining the fast C-s reduction. From the fact that the carbon precipitation rate is controlled not only by the self-interstitial generation, but also by the precipitate density, it is suggested that the generated interstitial carbon impurities are most likely to coprecipitate at common sites with O-i. (c) 2006 The Electrochemical Society.