Authors refer to not much known adverse reaction in treatment with betalactam antibiotics. In years 1997 – 1998 there was 691 children treated in our ICU, we found in 25 of them increased level of antibodies against betalactam antibiotics. Indication for examination of level antibodies was X-ray picture of wet lung, contemporary application of betalactam antibiotics and somet imes positive allergic history. Antibodies was determined with method of non direct hemaglutination and as a positive finding was level 1:320 and more. In these cases was antibiotic treatment changed to antibiotics of other type. We found recess of X-ray picture in 20 cases, 5 children died. Histological inv estigation for evaluation of immunocomplexes C3 and IgG in the wall of alveoli was made immediately post mortem. Immunofluorescent investigation findings were positive in 4 cases. Authors recommend in case of worsening of lung changes to evaluate level of antibodies and replace betalactam antibiotics with antibiotics of other type.

        Key words: betalactam antibiotics – level of antibodies against betalactam antibiotics – adverse effect of antibiotics – immunofluorescent investigation