Annealing of ion–implanted silicon was performed with a CO2 laser in two different modes of operation. In some experiments, short, 300 nsec pulses from a Q‐switched laser were used, in others CW irradiation with effective dwell times of the order of 1 sec. Rutherford backscattering and transmission electron microscopy measurements indicate that excellent crystalline structure may be obtained, with substitutionality of implanted As or Sb depending on laser parameters and substrate temperature. A considerable redistribution of implanted ions occurs in the pulsed operation of the laser, whereas long exposures result in no detectable change of implanted profiles. In the former case the surface morphology is characteristic of melting, in the latter lack of any surface features is consistent with regrowth in a solid phase.