A large amount of clinical evidences demonstrates a clear association between long-term and/or stress-related hyperglycaemia, and development of complications after surgery. The incidences of perioperative hyperglycaemia are demonstrated in 20-80 % of all cases depending on the type of elective surgery, with the h ighest rate registered in cardiac surgery. The most studied pathophysiological complications of long-term hyperglycaemia in Diabetes Mellitus (DM) patients are; activation of the polyol pathway, diacylglycerol/protein kinase C and hexosamine pathways, advanced glycation product formation, and oxidative stress. The uncontrolled stress-related hyperglycaemia during and after surgery instigates: osmotic diuresis with further fluid and electrolyte imbalance, increased gluconeogenesis and glucogenolysis, breakdown of fats into free fatty acid and glycerol, proteins into amino acids, and increases generation of pro-inflammatory cytokines. All these changes may lead to development of diabetic ketoacidosis, immune deregulation and insulin resistance. Some clinical investigations seems to indicate that anaesthesia with propofol may have some advantages in keeping of stable blood sugar over inhalational agents. Two clinical trials comparing the influence of different anaesthetic agents on perioperative glycaemic status in diabetic patients are currently underway. For better management of perioperative hyperglycaemia in diabetic patients under surgery we have proposed several important practical principles.