This study was performed to assess the value TTC assay in the diagnosis of biomaterial-associated infections. In this assay, soluble colourless TTC is reduced to insoluble red formazan by electron transfer associated with active oxidative bacterial metabolism and is precipitated intracellularly. Microbial adhesion and biofilm formation on the surface of medical prosthetic devices (vesicular and urinary catheters) made of various polymers (PTFE, H-PE, PCW, SL), were determined. The microorganisms which are most often isolated in medical device-associated infections: S. aureus, S. epidermidis, E. faecalis, E. coli, P. vulgaris, P. aeruginosa, C. albicans, were included into the study. The obtained results indicate that the assay using TTC as a metabolic indicator of bacterial biofilm presence, is technically simple to conduct with minimal setup time. Even when classical cultures yielded no bacterial growth, TTC assessments demonstrated bacterial biofilms. TTC assay could be recommended as a quick routine method for confirmation of biomaterial device-associated infection.