Acrylic and acetal resins as well as polished Cr-Co alloys used commonly as prosthetic materials were located in physiolog. sauna suspensions of Candida albicans fungi and Staphylococcus aureus, Enterococcus hirae, Escherichia coli and Pseudomonas aeruginosa bacteria for 60 min at 37 degrees C and then transferred to a humid chamber to study viability of the microorganisms during 5 days of incubation. P aeruginosa bacteria showed the highest survival rate on all the substrates studied. The no. of bacteria and fungi cultures on the acetal resin substrate was the lowest one.