This paper demonstrates the potential for cross contamination with bacteria and viruses from impression materials and evaluates the efficacy of four disinfection systems on irreversible hydrocolloid impressions contaminated with Streptococcus sanguis or poliovirus. An irreversible hydrocolloid impression was made of a contaminated acrylic resin template. The impression was disinfected and residual microorganisms were harvested by sonication, cultured, and counted. The results showed that the impression material could act as a vehicle for the transfer of both bacteria and viruses. Further, the virus was shown to be present in the body of the impression and under certain conditions may evade decontamination.