OBJECTIVES: To calculate in-hospital mortality after lobectomy for primary lung cancer in the United Kingdom; to explore the validity of using such data to assess the quality of UK thoracic surgeons; and to investigate the relation between in-hospital mortality and the number of procedures performed by surgeons. DESIGN: Retrospective study. SETTING: 36 departments dealing with thoracic surgery in UK hospitals. PARTICIPANTS: 4028 patients who had undergone lobectomy for primary lung cancer by one of 102 surgeons. MAIN OUTCOME MEASURES: In-hospital mortality in relation to individual surgeons, among all patients, and among each of five groups of patients defined by the number of operations performed by the surgeon. RESULTS: 103 patients (2.6%, 95% confidence interval 2.1% to 3.1%) died after surgery during the same hospital admission. No significant difference was found for in-hospital mortality between the five groups. CONCLUSIONS: The number of procedures performed by a thoracic surgeon is not related to in-hospital mortality. Reporting data on in-hospital mortality after lobectomy for primary lung cancer is a poor tool for measuring a surgeon's performance.