Some reports indicate that topical nasal treatment with capsaicin, which is usually effective in reducing symptoms of vasomotor rhinitis, may also reduce symptoms in patients with nasal polyps. The aim of this study was to investigate the effect of topical capsaicin treatment in severe sinonasal polyposis. Nine non-allergic, non-asthmatic patients with diffuse eosinophilic nasal polyposis were subjected to topical capsaicin treatment: for 3 consecutive days 0.5 ml 30 micromol/l capsaicin solution and on days 4 and 5 100 micromol/l capsaicin solution was sprayed into each nostril. Coronary computed tomography (CT) images were made shortly before treatment. Baseline nasal lavages and a questionnaire containing subjective symptoms and nasal endosocpy were taken just prior to the first application. Nasal lavages were performed prior to and after the last treatment and over 4 weeks, endoscopy and subjective scores at each weekly visit, and correspondent CT scans 4 weeks after the treatment. CT images were analysed by computer, calculating the nose sinuses air volume (NSAV) from the surface of aerated parts of nasal and sinus cavities for each slice per patient prior to and after treatment. Statistical analysis was performed comparing NSAV, subjective scores, endoscopy scores and eosinophil cationic protein (ECP) levels in nasal lavages prior to and after treatment. Topical treatment with capsaicin significantly increased NSAV and very significantly improved subjective and endoscopy scores, but did not significantly alter ECP levels in nasal lavages.