4He+ Backscattering and SIMS were used to study impurity redistribution during laser formation of refractory silicides. Thin films of Mo and W were evaporated on to <100> p-type silicon substrates, which were As or B implanted to doses of 1 ×1015 to 1 ×1016cm−2 . These samples were laser reacted with multiple or single laser scans at various powers. Analysis of these films indicate impurity movement into the forming silicide layer. Impurity concentrations in the films were observed to be as high as 7.8×1020 cm−3−> for As in WSi2 , however a reduction in this concentration occurred with subsequent thermal annealing.