The optical reflectivity from buried and exposed CoSi2 layers produced by Co ion implantation of Si substrates has been measured over the energy range 0.012–6.2 eV (0.2- 100 μm). Both unannealed and annealed layers were investigated. The complex dielectric constant of the bare CoSi2 layer was obtained from a Kramers-Kronig analysis. The plasma frequency, carrier concentration and relaxation time of the buried CoSi2 layers were obtained from classical dispersion analyses of the multicomponent reflectivity data. The effective carrier concentration derived from the optical data and the measured chaneling from Rutherford back scattering correlated with anneal temperature.