Recent developments should have aided to reduce postoperative complications of endoscopic sinonasal surgery: Computerised tomography (CT) and magnetic resonance imaging (MRI) allow a more precise preoperative view of the anatomic situation and possible variations. The Lund-MacKay-Index provides a tool to assess the extent of the disease, and by introducing microscopic-endonasal and computer-assisted sinunasal surgery (CAS) as well as providing the corresponding training technical progress has been made. We analysed the data of 2,596 patients with acute or chronic rhinosinusitis who underwent surgery between 2000 and 2005 using the procedure of Stammberger. We saw 3.1 % minor complications (minor bleedings, perforation of the lamina papyracea), 0.9 % major complications (severe bleedings, cerebrospinal fluid (CSF) leaks, lesion of the ductus lacrimalis), and one (0.04 %) serious complication (meningitis). When we compared these figures with those of reports from the late 90 s by correlating opacification, type of operation, the surgeon's experience and employing CAS with the outcome we did not find a distinct improvement in the rate of postoperative complications. Serious complications and those resulting in permanent harm such as carotid artery injury, cerebral deficit or death have, however, become very rare. A grading into I (minor), II (major) and III (serious) complications is proposed, to point out this critical grade-III proportion, which should not exceed 0.1 %.