This paper provides an overview on the current knowledge of chlamydiae prevalence in pigs. Within the order Chlamydiales are Gram negative obligate intracellular pathogens. The family Chlamydiaceae has recently been taxonomically revised and there are two genera proposed: Chlamydia and Chlamydophila. Organisms of both genera can be isolated from their specific animal hosts worldwide. In pigs C. suis, C. abortus, C. pecorum and C. psittaci have been isolated. Chlamydial infections in pigs are associated with different clinical diseases such as conjunctivitis, rhinitis, pneumonia, pericarditis, polyarthritis, abortion, stillbirths and reproductive disorders. Infections can be frequently asymptomatic, and the host serves as natural reservoir of the organisms. Diagnosis of swine chlamydiosis is rather rare, since most veterinary diagnostic laboratories do not perform routine examination for chlamydiae. Meanwhile, recent scientific reports present data, confirming that swine chlamydiosis can be an important health problem in swine farms and may cause significant economic losses.