Chlamydia trachomatis may cause a condition of inflammatory infection in several parts of the body. For example, the most common site is the eye infection, referred to as trachoma. If a patient with conjunctivitis is suspected of having trachoma, a relevant discharge test is done to look for the pathogen. A positive result for Chlamydia trachomatis will result in a definitive diagnosis of trachoma; a negative result will not rule out a trachoma diagnosis 100% of the time. Because the accuracy, and sensitivity of any test is not 100%, there is a certain rate of false positives and false negatives. This must be combined with the patient’s clinical features, such as characteristic conjunctival congestion, vascular blurring, a large number of follicles that can be seen in the eye, and corneal vascular opacities that can develop over time. In the diagnostic criteria of trachoma, positive Chlamydia trachomatis is not a necessary condition and the diagnosis is based on the typical clinical manifestations. Because of the many and serious complications of trachoma, treatment can be started if trachoma is suspected. The most sensitive drugs are macrolides, but in the case of Chlamydia, multiple types of antibiotics are relatively sensitive, and appropriate combinations can be considered. Chlamydia trachomatis may also infect the genitalia with urinary tract infections. Urine tests, especially urine cultures, can be performed to determine the presence of Chlamydia trachomatis infection. The main treatment modality is still antibiotics, which may be used systemically, and the drug treatment cycle is often long, at least 1 to 2 months in principle. In the case of negative Chlamydia trachomatis, a visit to the ophthalmologist is still required to consider the final diagnosis after a thorough eye examination.