Currently, acute respiratory infections (ARI) are obviously considered to be the most topical issue of pediatric practice. It is worth noted that the age peculiarities of immune system in preschool children stipulated their higher vulnerability to infections and less differentiated response against infection process compared to older children and adults. Research aim consisted in finding out significant factors which are closely associated with serum immunoglobulin (Ig) levels in preschool children against the background of recurrent ARI.