Rutherford backscattering (RBS) and transmission electron microscopy (TEM) have been employed to investigate the annealing behaviour of Pb-implanted Si layers. The dose dependence of the post-anneal, residual disorder has been examined in considerable detail. Results indicate that the ability for the implanted Si layer to reorder as a single crystal decreases with increasing Pb concentration contained within the amorphous surface layers. The reordered Si layer is completely polycrystalline for Pb concentrations greater than a few atomic percent and the formation of this polycrystalline structure during annealing is accompanied by substantial Pb outdiffusion. Our observations lead us to suggest a step-by-step representation for Si recrystallization, where the reordered structure is dependent upon the local Pb concentration encountered as the regrowth process progresses from the bulk towards the Si suface.