The purpose of this study was to evaluate the nosocomial infections in intensive care units. The infections encountered in Intensive Care Unit (ICU) of Internal Medicine Depertment of Ege University Hospital, December 2002-May 2003, were evaluated. from different aspects including agents of infections, antimicrobial prescribing, length of stay, rate of mortality and cost. Patients admitted to ICU were daily visited and data collected were recorded in a form. The diagnosis of ICU infections were established according to the Center for Disease Control and Prevention (CDC) criteria. The cost of each patient was found in the hospital computer record. Data were analysed with SPSS 11.0 program. Totally 138 patients (female: 71, male: 67, mean age: 53.37±18.32)) were investigated. Total length of stay of 138 patiens were 1467 days. Thirty eight infection attacks were observed in 29 patients. The incidence of infection was 21.0/100 and the incidence density was 25.9/1000. Intravenous catheter related blood stream infection was the most common infection (13/38). The rate of mortality was 24.1%. Only 26.0% of patients did not use antibiotics. When the indication of infection, antibiotic prescription, doses and length of usage of antibiotics were considered, it was seen that in 48.0% of the patients antibiotic usage was inappropriate. The length of stay in ICU was 9.85±6.99 days, much longer in patients who developed infection than in those who did not. The cost also was found higher in patients with infection [patients with ICU infection; 9.776±5.997 billion Turkish liras (6517.33±3998.00 $), patients without ICU infection 6.492±7.474 billion Turkish liras (4328.00±4982.66 $) (p<0.05)]. In conclusion, it was seen that the ICU infections are the major cause of long stay and high cost in the hospital. The principle of rational antibiotic use in ICU is the most important issue to reduce the occurence of resistant bacterial infections as well as cost.