Acute upper respiratory tract infection (URTI) is a common disease in young children. URTI contributes to approximately 20% of mortality in children younger than 5 years of age. Infections of the upper respiratory tract are the most common cause of viral morbidity in children. They represent the most frequent problem in general pediatric practice and are responsible for more than one third of school absences. On the other hand respiratory tract infections through MALT system play a positive role in maturation and development of immune system. Many different immunologic disturbances can occur during the development of respiratory infections. Disorders of granulocyte functions are the principal cause of inflammation in the upper respiratory tract. Chemiluminescence of granulocytes is a renowned method for the estimation their overall activity as measured by the production of reactive oxygen species. The goal of the study was to evaluate chemiluminescent activity of granulocytes from 41 children with recurrent infections of the respiratory tract compared to 30 healthy children. Chemiluminescent response to all the examined stimuli in children with recurrent infections was significantly lower compared to control. In the examined group of 41 children depressed response to at least 1 stimulus was detected in 32 (78%) cases. The use of both fMLP and opsonised zymosan allowed to detect defect of granulocyte function in 93,75% cases. This defect may be related to delayed maturation of the immune system in certain children or may be induced by intensive therapy with antibiotics.