The main purpose of this study was to evaluate the anticariogenic effect of argon laser. Histological observations on lesion initiation and progression were performed under the polarized microscope. The results from the present study can be summarized as follows; 1. The specimens of laser cured group were shown to have more irregular and discontinuous lesion body in general than visible light cured group with rather continuous positive birefringence. 2. With lesion initiation and progression, almost all the specimens showed deeper body of lesion with shallower intact surface zone in the visible light cured group than the laser cured group(p<0.05). When the comparision was made between the two argon laser cured groups, the single-cure group showed deeper lesion body and the shallower surface layer than double-cure group. 3. Based upon the above mentioned results of this study, it can be assumed that the use of argon laser in the procedure of resin polymerization may provide the child and adolescent patient population with anticariogenic effect as well as efficient polymerization. Further studies using various materials and experimental conditions are being encouraged.