This review discusses several aspects of surgical quality assurance: 1. The surgical audit to collect data and analyze postoperative complications. 2. Quality assurance by measurement of patients' postoperative long-term outcome. 3. The elaboration of therapeutical guidelines. 4. Measurement of costs and benefit of the surgical intervention including patients' postoperative quality of life. 5. Quality assurance of clinical trials and medical publications. It is demonstrated that the regular documentation of postoperative complications and an internal data analysis improve the results, dependent on the quality of the data which is best guaranteed by a neutral observer. The late results after operation are mainly influenced by the quality of the surgeon, as prove recurrence rates after hernia repair ranging between 0 and 10% using identical operation techniques, or locoregional recurrences of 30-60% after abdominal perineal resection of the rectum. The elaboration of therapeutical guidelines may be helpful for the evaluation of the benefit of the intervention and for the prevention of unnecessary operations as has been demonstrated for the treatment of symptomatic and asymptomatic carotid artery stenoses. Qualified clinical studies performed according to the GCP rules with biometrical planning, clear cut definition of the purpose of the study and listing of inclusion and exclusion criteria are the prerequisites of substantiated therapeutical guidelines. Under increasing economic pressure not only the benefit, but also the costs of treatment are of major importance, the evaluation of the cost effectiveness ratio by measuring the cost per quality adjusted year of life saved will become essential for future therapeutical recommendations.