Stannous fluoride has been shown to be an effective chemotherapeutic agent in combating tooth decay. While various mechanisms have been proposed to explain this anticavity activity, only recently have we begun to learn what the actual products of the reaction between stannous fluoride and calcium and phosphate ions are. It is the objective of this project to extend the recent studies in this area by investigating the SnF2 - Ca(OH)2 - H3PO4 system. These studies will be carried out both at natural pH and constant pH. This system should provide a closer approximation to the oral environment than the stannous fluoride-apatite system does. The products of these reactions will be identified by application of X-ray diffraction, infrared, atomic absorption, and wet chemical analytical methods.