Thermal stability of rapidly annealed CoSi2/n-GaAs and CoSi2/p-InP contacts was studied. Annealing time was 10 s and the proximity method was used during annealing. Annealing at 700 and 800 degrees C made contacts more reliable, which is related to the removal of sputter created defects. Annealing at temperature higher than 900 degrees C caused significant degradation, which is attributed to the diffusion and reaction of elements at the interface.