An analytical model is presented for solid‐phase reactions induced by a scanning cw laser. The results are applicable for both rate‐limited reactions, such as the regrowth of implanted amorphous Si, and diffusion‐limited reactions, such as the formation of metal silicides. The effect of the laser is interpreted in terms of a furnace anneal at an ’’effective temperature,’’Teff, for an ’’effective time,’’teff.Teffis shown to be equal to the maximum laser‐induced surface temperature, whileteffequals the laser dwell time multiplied by a ’’dwell‐time reduction factor’’ which is a rational function of several material and annealing parameters and is typically on the order of(1)/(3) . A comparison of theory and experiment is made for the specific case of the formation of Pd2Si.