SummaryChronic rhinosinusitis' pathogenesis is not completely established and there are some explanations for this disease, such as osteitis, superantigens, fungal-mediated hypersensitivity and, more recently, biofilms. There are no reports in Portuguese about biofilms in chronic rhinosinusitis.AimTo reproduce a method for visualization of biofilms in patients with chronic rhinosinusitis and nasal polyps.Patients and MethodsSamples of ethmoid bulla of nine patients with chronic rhinosinusitis with nasal polyps without response to clinical treatment who underwent surgery were analyzed with scanning electron microscopy to evidence bacterial biofilms.Study designA contemporary cross-sectional cohort studyResultsIn 55.56% (5/9) of the patients we observed biofilms by seeing three-dimensional structures, spherical structures surrounded by an amorphous matrix and water-channels.ConclusionWe reproduced a method for visualization of bacterial biofilms by scanning electron microscopy and evidenced its presence in chronic rhinosinusitis with nasal polyps.