Background. The CRP value alone is not sufficiently reliable for the diagnosis of invasive bacterial infections. Aim. Measurment of serum concentration of CRP and other routinely measured acute reactants of inflammation together with clinical signs is very useful in differentiating between a bacterial and viral infection. Methods. Our retrospective research included 333 children aged 0 to 14 years who were diagnosed with »febrile status« in 2003 and referred to the University Medical Center, Department of Infectious Diseases in Ljubljana. For a more comprehensive classification of invasive bacterial infections, additional 26 records from 2004 and 2005, in which the diagnosis was either bacteremia or meningitis. In order to compare the values of the bacterial and viral infections, the Student’s t-test, Mann-Whitney U-test and chi-square test were used. The differences were considered statistically significant when the level of risk was lower than 0.05 (p < 0.05). To compare sensitivity and specificity, PPV and NPV of acute infection indicators the ROC curve was used. Results. The most effective way of differentiating between a bacterial and a viral infection is to measure both the CRP value and the total number of leukocytes. It is also important to monitor the clinical picture, especially concerning conjunctivitis. Acute inflammatory indicators are normally just as high with adenovirosis in children as they are with bacterial infections. However, new recommendations concerning the treatment of individual clinical syndromes should be made. In this manner, the use of antibiotics could be reduced by 10.3%.