We have quantitatively analyzed the structure and the annealing behavior of the point defects introduced by ion implantation in Si. We used deep-level transient spectroscopy to monitor and count interstitial-type (e.g., carbon–oxygen complexes) and vacancy-type (e.g., divacancies) defects introduced by MeV Si implants in crystalline Si and to monitor their annealing behavior for temperatures up to 400 °C. A small fraction (∼4%) of the initial interstitial–vacancy pairs generated by the ions escapes recombination and forms equal concentrations of interstitial- and vacancy-type room-temperature stable defect pairs. At T≤300 °C, vacancy-type defects dissociate, releasing free vacancies, which recombine with interstitial-type defects, producing their dissolution. This defect annihilation occurs preferentially in the bulk. At temperatures above 300 °C, all vacancy-type defects are annealed and the residual damage contains only ∼3 interstitial-type defects per implanted ion. This imbalance between vacancies and interstitials is not observed in electron-irradiated samples, demonstrating that it is the direct consequence of the extra ion introduced by the implantation process. © 1997 American Institute of Physics.