Remineralization of enamel lesions in vitro by use of sequential treatments with an alkaline (pH 9) phosphate (1mol/L) solution and slightly acidic (pH 6) calcium (1mol/L) solution was reported to be relatively ineffective. An analysis of the diffusion processes that may occur during the remineralization treatments suggested that the driving force for diffusion of Ca into the lesion can be increased by making the calcium solution more alkaline than the phosphate solution. In the present study this modified treatment procedure was evaluated for remineralizing root lesions in vitro. Results show that (1) in the control group there was a slight increase in mineral density in the surface region of the lesion, (2) in the experimental group there were significant (p<0.05) increase in mineral content in the outer 40μm of the lesion, and (3) in contrast to the finding reported previously, thick mineral deposits on the surface of the root were not observed.