Computer aided surgery has been used in the Department of Otolaryngology--Head & Neck Surgery, Rigshospitalet, Copenhagen since October 1998, and is now a regular supplement to conventional functional endonasal sinus surgery (FESS) and management of anterior skull base lesions. This technique was designed to enhance surgical precision and thoroughness and to reduce complications. Since this is a new technique, the clinical findings and surgical outcome are prospectively collected in a database. Results for conventional FESS are entered in the same database for comparison. The aim of this study is to present a standardized Danish database.