Chlamydia trachomatis may be an important cause of lower respiratory tract infection (LRTI) in infants born to mothers amongst whom there is a high prevalence of sexually transmitted disease. A study of 100 ambulatory infants with signs of LRTI in South Africa showed that 6% had C. trachomatis infection. The majority of the infected infants had received chloramphenicol eye ointment as prophylaxis. Half had previously visited a health facility for the same illness but the infection has been misdiagnosed. Infants with C. trachomatis infection were According to the Centers for Disease Control (CDC) guidelines, 85% were younger than uninfected infants (mean (SD) age of 3.8 weeks (3.2) vs 8.7 weeks (5.4); p=0.03). Clinical signs significantly associated with chlamydial infection were the presence of eye discharge (p = 0.02) or conjunctivitis (p = 0.01). There was a greater rate of rhinorrhoea (p = 0.06) and wheeze (p = 0.03) amongst patients without chlamydial infection. H. influenzae, M. catarrhalis, S. pneumoniae, S. aureus and N. gonorrhoeae were cultured from five different patients infected with chlamydia. The majority of infants with chlamydial infection had mild disease requiring only outpatient anti- biotic therapy.