Bacteria are now recognised as existing in two forms--free floating (planktonic) or in sophisticated communities called biofilms. Bacteria within biofilms are difficult to culture and highly refractory to antibiotic treatment. Biofilms could explain some of the paradoxes associated with chronic rhinosinusitis. Many patients are refractory to antibiotic therapy, bacteriology culture swabs frequently do not grow bacteria and positive bacteriology swabs often do not correlate with clinical findings. As antibiotics are largely ineffective in the treatment of bacterial biofilms, alternative therapeutic strategies including blocking molecular communication (quorum sensing) between bacteria, inhibiting biofilm matrix production and interventions that damage bacterial membranes are being explored as treatment options. So far these approaches have been largely unproductive. While physical therapies such as short wave diathermy and therapeutic ultrasound have been advocated as treatments for rhinosinusitis for many years, critical evaluation of these therapeutic interventions is virtually non-existent. Until recently any benefit has been difficult to explain using conventional microbiological paradigms. However, in the laboratory setting ultrasound enhances the killing of bacteria in biofilms both in vitro and in animal models. The successful application of ultrasound to sinus disease could mean the development of a new paradigm in our treatment of chronic rhinosinusits, a reduction in antibiotic resistance and improved medical management with a subsequent reduction in surgical intervention.