The paper contains a review of the literature on the correlation between Chlamydia trachomatis infection and CIN as well as invasive cervical cancer. This infection is not only responsible for inflammation (very often occult) in the upper genital tract and PID but also is probably one of the causes of cervical hypertrophy. In high percentage of CIN Chlamydia trachomatis infection is present. This pathogen especially serotype G, I and D is strongly associated with development of invasive cervical cancer.