The association between asthma and sinonasal disease has been known for years. Effective treatment of sinonasal disease, which is one of the factors that exacerbate asthma, may also improve and stabilize the asthmatic condition. This study examines the outcome of functional endoscopic sinus surgery (FESS) on asthmatic patients with massive nasal polyposis. Thirty-four asthmatic patients were included in the study. All were operated on in our department and were analysed for pre-operative data regarding their asthma and sinonasal disease. A questionnaire regarding subjective evaluation of asthma and sinonasal status was presented to the patients, and objective evaluations, including nasal endoscopy and spirometry, were performed. Follow-up endoscopy revealed satisfactory results in 88 per cent, with positive correlation to the patients‘ subjective assessment of nasal status. No such correlation was found with regard to subjective and objective assessment of asthma: a small group of patients had completely clean sinonasal cavities with no perceived improvement in their asthmatic condition. The use of prednisolone and bronchodilators was significantly reduced post-operatively. However, in a subgroup of 13 patients followed at the asthma clinic, who had adequate pre-operative and post-operative data, there was no difference in their pre- and post-operative asthma condition. Seven had minimal improvement and in six there was a definite worsening of their asthma; nevertheless, nasal breathing and quality of life improved in most patients. The mean follow-up was 2.1 years. Thus, we conclude that in this study FESS does not improve asthma, but does improve the quality of the life of the patient.