Patients who drink too much have more complications after surgery. The aim of this thesis was to evaluate the evidence, possible mechanisms, and prevention of the increased postoperative morbidity in alcohol abusers, defined by a consumption of at least five drinks per day. The literature could be criticised for several methodological flaws. Nevertheless, the results are in agreement showing moderate to strong evidence of increased postoperative morbidity after surgical procedures on alcohol abusers. There is weak to moderate evidence of increased postoperative mortality, hospital stay, and re-operation. The personal and economic consequences are tremendous. The incidence of alcohol abusers undergoing surgery was 7% to 49%, according to gender and diagnosis. They have been identified by a self-reported alcohol intake, which implies the possibility of underestimation. Alcohol markers could be used for a more precise identification of alcohol abuse. However, the inability of the questionnaires to detect short-term changes in intake and abuse without dependence, the inconsistent predictive values of the biological markers, and the lack of evidence of an association to postoperative morbidity reduces their usefulness. A detailed alcohol history is therefore recommended. The pathophysiology may include alcohol-induced organ dysfunctions. We demonstrated that subclinical cardiac insufficiency, immune incompetence, and haemostatic imbalance were already present preoperatively. A relation between the various lesions remains to be investigated. The surgical stress response was greater in alcohol abusers, which may further compromise the already dysfunctioning organs, thus leading to the documented increase in postoperative morbidity. Withdrawal from alcohol reverses organic dysfunction in non-surgical patients. Haemostasis normalises after one to four weeks, cardiac function after one month, immune function after two months, and response to external stress after three months. Accordingly, our small randomised investigation has shown that one month of abstinence before surgery improves several organic dysfunctions and reduces postoperative morbidity. We have demonstrated that prevention before surgery is possible. The study has methodological flaws, so further studies are required before final recommendations can be given. However, in the meantime clinical guidelines for alcohol abusers undergoing surgery should include up-to-date patient information and four weeks of abstinence before surgery, in accordance with the evidence-based association, the potential prevention attained by preoperative abstinence, and the best clinical practice. Implementation should be monitored in the clinical databases. In future, all patients admitted to surgery should be offered a health promoting dialogue with the surgeon, anaesthesiologist, general practitioner, or other health professionals, which focuses on alcohol among other risk factors in relation to the operative treatment, diagnosis and prognosis. A beneficial effect attainable from this multi-modal prevention and fast track surgery should be investigated among the alcohol abusers.