Objectives: This study summarises the results of a National Audit of sino‐nasal surgery carried out in England and Wales. It describes patient and operative characteristics as well as patient outcomes up to 36 months after surgery. Design: Prospective cohort study. Setting: NHS hospitals in England and Wales. Participants: Consecutive patients undergoing surgery for nasal polyposis and/or chronic rhinosinusitis. Main outcome measure: The total score derived from a 22‐item version of the Sino‐Nasal Outcome Test (SNOT‐22). Lower scores represent better health‐related quality of life. Results: A total of 3128 consecutive patients at 87 NHS hospitals were enrolled. There is a large improvement in SNOT‐22 scores from the pre‐operative period (mean = 42.0) to 3 months after surgery (mean = 25.5). The scores for patients undergoing nasal polypectomy improved from 41.0 before surgery to 23.1 at 3 months after surgery, while the scores for patients undergoing surgery for chronic rhinosinusitis alone improved from 44.2 to 31.2. The SNOT‐22 scores reported at 12 and 36 months after surgery were similar to those reported at 3 months. Excessive bleeding occurred in 5% of patients during the operation and in 1% of patients after the operation. Intra‐orbital complications were reported in 0.2%. Of those patients undergoing primary surgery for bilateral grade I or II polyposis, 18% had not received a pre‐operative course of steroid treatment. At the 36‐month follow‐up, 11.4% of patients had undergone revision surgery. Conclusions: The audit confirms that sino‐nasal surgery is generally safe and effective. There is some evidence that patient selection for surgery could be improved.