The examination of 169 children aged 3-15 years admitted to ENT department for exacerbation of chronic adenoiditis has shown high chlamydial contamination of the pharyngeal mucosa. Identification of chlamydial structures and specific antibodies was performed with application of direct (polymerase chain reaction, immunofluorescence) and indirect (EIA) methods. Specific structure of the verified pathogens as well as clinical manifestations of adenoiditis associated with chlamydial infection and characteristics of immune response of the child to chlamydia are described.