Purpose: Dental impressions often carry microorganisms that may cause cross infection from patients to dental staff. The aim of the current study was to determine the effectiveness of 4 different disinfectant solutions on 3 commonly used impression materials—alginate, polyether, and polyvinyl siloxane—to establish a protocol for disinfection of these impression materials after clinical exposure and prior to handling in the dental laboratory. Materials and Methods: A total of 45 impressions were taken from the maxillary dentate arches of 15 dental staff participants at the Department of Dentistry, Prince Rashid Hospital, Irbid, Jordan. For each participant, 3 successive impressions were recorded in the different impression materials. For each impression, 6 specimens were dissected from 6 different locations and exposed to 6 different regimens: 1 was left untreated, 1 was immersed in sterile water for 10 minutes to serve as a control, and the remaining 4 specimens were exposed to 4 different disinfection treatments (Dimenol, Perform-ID, MD 520, and Haz-tabs). Serial dilutions of the suspension were carried out and counted by the Miles-Misra technique (inoculation on Columbia blood agar for quantification). The dilutions were aerobically incubated at 37°C for 48 hours. Results: The disinfectants were able to completely eliminate microorganisms carried by the impressions. For those undisinfected specimens, the results showed that untreated alginate impressions appear to carry more microorganisms (P < .05) than the other 2 rubber impression materials used in the study. For those specimens immersed in sterile water for 10 minutes (control group), the number of microorganisms eliminated was increased from 62% to 90% compared to those left untreated. Conclusion: Impression materials may act as a vehicle for the transfer of microorganisms from the patient’s mouth to dental personnel. Impressions should be disinfected to eliminate the risk of cross contamination. Int J Prosthodont 2007;20:299–307.