The bacterial biofilm theory which describes bacterial populations in natural and pathogenic ecological systems in terms of a free-floating or 'planktonic' population of bacteria interacting with a more important matrix enclosed 'sessile' population of bacteria associated with or adherent to a surface, may help explain some of the problems linked to our understanding the nature of urinary tract infections. This paper reviews the role of bacterial biofilm formation in catheter-associated infection, prostatitis and struvite (infected stone) calculogenesis stressing, the importance of bacterial biofilms in the pathogenesis, persistence and hence the treatment of urinary tract infection.