Chlamydia infection is a current problem and is one of the most common sexually transmitted infections. Untreated, it leads to serious complications. The causative agent of the disease is the microorganism Chlamydia trachomatis. It is an intracellular microbe, with serotypes D to L causing sexually transmitted diseases. After infection with chlamydia, microorganisms enter the cells of the mucous membranes of the genital tract. They begin to divide and become metabolically more active forms called reticulation bodies. After 72 hours of being in a cell, chlamydia induces cytolysis (cell death) and is ready to infect others. Chlamydia is transmitted from person to person through direct contact between mucous membranes. Infection does not always lead to the development of a clinical picture. For example, in France, asymptomatic carriage in the cervical canal and urethra reaches up to 25% in women and up to 70% in men of sexually active age: 15-25 years. If symptoms do occur, Chlamydia trachomatis causes gonococcal-like diseases—urethritis, cervicitis, epididymitis, prostatitis, conjunctivitis, perihepatitis, Reiter’s syndrome, and pelvic inflammatory disease. BOX_MORE_NEWS Endocervicitis is the most common inflammation caused by chlamydia in women. Most of the infected are asymptomatic. In the remaining cases, an inflammatory response is induced. Yellow mucopurulent discharge and the tendency of the mucous membrane to bleed are alarming symptoms that require special attention and consultation with a doctor. Left untreated, chlamydia can ascend (ascend) up the female genital tract. The uterine cavity (endometritis) and fallopian tubes (endosalpingitis) become inflamed. Pelvic inflammatory disease is characterized by the so-called endometrial syndrome. It presents with vaginal bleeding, dull abdominal pain, and uterine tenderness without an increase in the peripheral blood leukocyte count. Pelvic inflammation can spread to the liver, where adhesions form around its capsule. There is additional pain in the upper right quadrant of the abdomen and tenderness on palpation of the liver. This is called Fitz-Hugh-Curtis syndrome. Untreated chlamydial infection leads to sterility. Chlamydia trachomatis is the most important microorganism in the genesis of obstructive tubal sterility. It is estimated that after just one episode of pelvic inflammatory disease, about 10% of women suffer from infertility due to blocked tubes. The risk increases dramatically after each subsequent episode. Proper antibiotic treatment is doxycycline 100 mg, twice for at least 10 days. Macrolides are an alternative. Macrolides such as erythromycin can also be used during pregnancy because they do not cross the placental barrier. In the treatment of combined infection with gonococcus – see the article “Gonococcus”.