In 12 out of 66 children (18.2%), hospitalised at the Department of Pediatric Nephrology of the Medical Academy of Wrocław, Poland, the presence of Chlamydia trachomatis was detected in the urinary sediment. The tests were made using an enzyme-linked-immunoassay, ELISA. These results are in 96.9% agreement with the results obtained by urethra swabs.