Diabetic ketoacidosis (DKA) and nonketotic hyperosmolar hyperglycemic state (NHOK) are acute complications of diabetes mellitus (DM). The aim was to investigate precipitating factors, therapy and the result of the treatment of DKA and NHOK. The study included all the people who were admitted to the Clinical Department of Endocrinology, Diabetes and metabolism disease KBC "Zvezdara" in the state of DKA and NHOK between 2007 and 2010. During this period we treated 56 people, aged 51.8 ± 18.8 years. DKA was diagnosed in 54 patients, whereas NHOK was diagnosed in two patients. Type 1 DM was present in 26 (46.42%) patients and type 2 in 30 (53.57%) patients. In DKA average values of glucose were 32±8,85mmol / l, HbA1c-11.6±2,52%, pH 6.89±0,17, HCO3-7.40±5,03. In patients with NHOK average glucose was 60.35±15,14mmol / l, HbA1c-11.2±1,7%,pH 7.43±0,1, HCO3-19, 8±5,23. There was a significant difference in the glucose level (t(54) =6.03,p<0.01) as well as in bicarbonate level (t(54)=3.72,p=0.01) between DKA and NHOK. The most common precipitating factors were: infection in 26 (46.42%) cases, inadequate therapy in 24 (42.85%) cases, myocardial infarction and cerebral stroke in 2 (3.57%) cases. All the patients with NHOK and 16 with DKA had previously been on oral antihy-perglycemic drugs, while 29 patients with DKA had previously been on insulin therapy. Upon admission, the previous therapy was not in relation with the level of glucose and pH. Bicarbonate level was significantly higher in the group treated with oral therapy (t (43) = 2.16,p <0.05). The therapy was considered because of rehydration, fractionally giving boluses HM insulin, potassium compensation and treatment precipitating factors. Rehydration was achieved with an average of 5.6±1,65 liters on the first day,4.08±0,87l on the second day, and 3±0,01 liters on the third day of infusion solutions. The total daily dosage of insulin bolus HM on the first day was 81.04±27,97i.j, 59.64±17,60i.j. on the second day and 58.06±19,70i.j. on the third day. Maximum daily supplementation of potassium in the form of 7.4% KCL solution was 61±18,70mmol / l. Upon the end of the treatment, the total of 26 (46.42%) was discharged on basal-bolus human insulin therapy, 18 (32.14%) on the treatment of basal-bolus analogues, 11 (19.64%) on therapy insulin premix and metformin, while two (3.57%) were discharged on oral antihyperglycemic medications. The treatment outcome was successful in 50 people (89.3%), while death occurred in 6 (10.7%) cases. The most common complication was hypokalemia, present in 29 (51.78%) patients. Other complications were acute renal failure (3 people), acute respiratory distress syndrome (2 people), pulmonary edema (2 people) and gastrointestinal bleeding (1 person). Despite education and available medications for diabetes, acute complications of diabetes can still occur and are sometimes accompanied by dangerous complications.