Statement of Problem: Infection control is the main step of prevention in dentistry. Effects of disinfectant solution must be evaluated in this process.  Purpose: The aim of this study was to evaluate the disinfecting effect of Deconex (solarsept), Cidex, and Micro 10 on high and low speed handpiece surfaces after cavity preparation.Materials and Methods:  In this experimental study, 105 specimens were obtained from surfaces of high and low speed handpieces after cavity preparation by sterile swab and were divided into 7 groups. Each group contained fifteen specimens which were carried to thioglycolate media. Samples were incubated and remained for 48 hours at 37oc. Microorganisms were cultured in different media, and the rate of microbial growth were calculated.Results: Following the various stages of investigation, it was found that all specimens from the surfaces of high and low speed handpieces, after cavity preparation, were infected, but no microbial growth and colony formation were detected after disinfecting the surfaces by disinfectants solutions used in the study.Conclusion: By evaluation of various sampling stages and microbial cultures in this study, it was concluded that the three disinfectants were able to destroy specific kinds of microorganisms after cavity preparation procedures, if they were provided and used by manufacturer instructions in order to decrease infection transmission.Key words: Disinfection, Deconex (Solarsept), Micro 10, Cidex