The objective of the present study was to develop a system of laboratory diagnostics ofchlamydial infection in the mucous membrane of the nose and paranasal sinuses in the patients presenting with chronic sinusitis. A total of 168 subjects at the age varying from 18 to 65 years were available for the examination based at the Department of Otorhinolaryngologyduring the period of exacerbation of chronic sinusitis. Chlamydia were identified by simultaneously using two direct (polymerase chain reaction and direct immunofluorescence) and one indirect (immunoenzymatic assay) methods. The study has demonstrated the high degree of probability of the detection of chlamydial infection based on the above complex of the laboratory methods. It is concluded that the use of the proposed algorithm in practical medicine makes it possible to improve the quality of laboratory verification of chlamydial infection and thereby to choose the adequate diagnostic strategy for the patients suspected of having chlamydial infection and to evaluate the effectiveness of the therapeutic measures being taken.