Objective: To investigate the dimensional changes and the surface quality of dental impression materials after disinfection with 3 chemically different agents. Method and Materials: Four alginate impression materials and 1 addition silicone material were selected. The impressions were made from a brass model simulating a 3-unit fixed partial denture. The chemical disinfection was performed with 3 different disinfectants for 10 minutes. Three samples of each impression material and disinfectant agent were investigated. As a control, 3 impressions of each material were made without any disinfection. The casts were made with a type IV dental stone. For each cast, 6 diameters and 3 distances were measured. To evaluate the dimensional stability, measurements were taken at a magnification of 343 with a light microscope. The surface quality was recorded using a profilometer. Results: The dimensional change and surface quality differed minimally; however, statistically significant differences were found between alginate and addition silicone impression materials (ANOVA, P .05). Casts from the silicone impressions were more accurate than the casts from alginate impressions. Conclusion: Different impression disinfection methods have only a marginal influence on dimensional stability and surface quality of dental casts. To achieve a higher precision, the use of an addition silicone can be recommended. Keywords: addition silicone, alginate, dental impression materials, dimensional stability, disinfection, surface quality