Evaluation and research of quality factors in surgery necessitates the consideration of 3 types of indicators: indicators of structures, indicators of processes and indicators of outcomes. We used these 3 types of indicators to assess the quality of thyroid surgery and to evaluate quality indicators. These studies allowed us to demonstrate the importance of a permanent monitoring of the outcomes of the thyroid surgery and the presence of human and organizational factors in the mechanisms of the surgical complications. This type of evaluation and research in quality of health care should be extended to all the surgical subspecialties.