The aim of the study was to assess the appropriateness of the provision of surgical treatment in the day hospital setting and at the same time to evaluate the efficacy of the service provided. The study was conducted on admissions to a day care unit operating in conjunction with the surgery division of a university hospital. The evaluation of appropriateness was carried out using explicit criteria, based on regional regulations and on guidelines drawn up by the Agency for Regional Health Services. The criteria related to the hospital bed equivalent Rotation Index and to the types of DRGs treated and services provided. Efficacy was assessed using the following para-meters: number of US-guided fine needle aspiration biopsies; techniques used; age, sex and nodule size; patient distribution by results of diagnostic examination; cytological classification; percentage of patients with complications. We also evaluated the possibility of transferring short-term (2-3 days) surgical admissions from ordinary regimens to the day care setting. The results of this study yield useful synthetic indicators for assessing the appropriateness both of the day care function as a whole and of individual operating units, providing both administrative and medical staff with a useful frame of reference for the planning of health-care management.