Aim: Rational antimicrobial use is important not only for the effectiveness of the treatment but also to prevent spread of antimicrobial resistance and to decrease hospital cost. Since accurate data about the appropriateness of antimicrobial prescription among children in hospitals in Turkey, we aimed to determine the situation in Hacettepe University Ihsan Dogramci Children's Hospital as a tertiary-care center. Data on use of antimicrobials were collected and evaulated in one day and it was determined that 104 (50,4%) of the hospitalized children were receiving antimicrobial treatment. The most common inappropriate use of these drugs was in neonatal (60,0%) and surgical (41,9%) wards. The highest rate of incorrect dosage was observed also in surgical wards (22,6%). Overall, irrational antimicrobial use was seen in 25,7 % of the patients and incorrect dosage was seen in 17,9 %. Inappropriate use was lower when an infectious disease specialist prescriped the drugs (10,8%) than in the other patients (43,1%) (p=0.0001). The duration of hospitalization was longer among children receiving antimicrobials. It can be suggested with these results that, in order to decrease the rate of inappropriate use of antimicrobials; educational studies and consultation with an infectious disease specialist, especially in surgical wards, may be effective.