Statement of Problem: Immersion in chemical disinfectant solutions have been recommended for impression disinfection. However, a recent approach involving microwave radiation disinfection of impression material has been suggested by some authors. Purpose: The purpose of this study was to evaluate the efficacy of microwave disinfection and its effect on dimensional stability of polyether impression material. Materials and Method: Polyether impression material was selected for study. Efficacy of microwave irradiation for 7 minutes at 720 watts and 2% glutaraldehyde for 30 minutes as disinfection procedures was evaluated against test organisms Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. Dimensional changes due to microwave and 2% glutaraldehyde disinfection were evaluated according to American Dental Association Specification no. 19. Data were analyzed by performing t test. Result: Microwave irradiation and 2% glutaraldehyde were effective in reducing the number of colony forming units (CFU) per unit volume (mL) for all the tested microorganisms compared with the control. Dimensional changes due to microwave and glutaraldehyde disinfection were 0.299% and 0.072% respectively. Conclusion: Both disinfectant methods i.e. microwave irradiation and 2% glutaraldehyde solution were effective against microorganisms tested when compared to control. Dimensional changes seen in microwave radiation and 2% glutaraldehyde disinfection were well within the maximum dimensional change permitted according to ADA specification number 19 (0.5%).