Chlamydia trachomatis represents one of the most common causative agents of sexually transmitted diseases. Clinically, genital chlamydial infections are similar to gonorrhoea. Although the clinical symptoms in chlamydial infections are usually milder than those in gonorrhoea, late complications are more common and more dangerous, because the carriers may easily escape notice. The knowledge of chlamydial infections has increased during the last few years. The present report deals with recent developments in this field.