Microwave sterilization techniques have previously been discussed in the literature, but there is need for information regarding the stability of acrylic resins subjected to these techniques. The purpose of this investigation was to measure and determine the potential influence of microwave sterilization on the dimensional stability of polymerized acrylic resin denture base materials. Uniform samples of previously heat-polymerized, autopolymerized, and visible-light-polymerized acrylic resins were measured for changes in weight and length before and after microwave exposure. All three acrylic resin materials maintained excellent stability; all materials had shrinkage values in the range of 0.02% to 0.03%. This is clinically insignificant compared to polymerization shrinkage, which averages 0.2%.