There is a concern that long-term immersion of impressions in disinfectant solutions may cause changes in the dimensions of the resulting stone casts. This study investigated the dimensional changes in stone casts resulting from immersion of five brands of addition-type silicone rubber impressions in disinfectant solutions for 30 min and 24 h. Impressions of a master cast designed to simulate an abutment tooth were immersed in 2% glutaraldehyde and 0.55% ortho-phthalaldehyde. The diameter of the stone cast was measured using a laser scan micrometer. For four brands of impression materials, 30-min immersion in disinfectant solutions produced no dimensional changes in the stone casts. For four brands of impression materials, 24-h immersion caused a significant decrease in the stone cast dimensions.