Aims: To evaluate the effect of the microwave disinfection on the dimensional changes of the heat–cured acrylic resin. Materials and Methods: Heat–cured acrylic resin was used in this study. Thirtytwo disk–shaped specimens with reference points were prepared to evaluate the linear dimensionalchanges of the heat–cured acrylic resin that sterilized by microwave irradiation and by chemicalsolutions chlorhexidine and sodium hypochlorite. The specimens were divided into four tested groups,eight specimens for each group. Group I as control group and other groups divided according to thesterilization method. The dimensional change was evaluated with an Electronic Digital Caliper. Meanvalues wear compared statistically with: One–way Analysis of Variance (ANOVA), followed byDuncan's Multiple Range Test to determine the significant different among the tested groups at(p≤0.05) level of significance. Results: They showed that there was a highly significant difference ofthe means values of the linear dimensional change among the four tested groups. Specimens sterilizedby microwave irradiation have a higher value than that sterilized by the chemical solutions.Conclusions: The results of this study appeared that sterilization by the microwave irradiation producea significant effect on the dimensional stability of the heat–cured acrylic resin, while sterilization bychemical solution produce no significant difference.