Almost 11,000 cases of Chlamydia trachomatis (CT) are diagnosed every year in Denmark. The most important epidemiologic factor is age under 25 years. The prevalence of CT among women applying for legal abortion is five to eight percent and in a recent study the prevalence of CT among second trimester pregnant women was found to be 2.9 percent. The consequences of CT-caused infections are many, including risk of infertility, ectopic pregnancies, perinatal transmission etc. The perinatal transmission rate is high in untreated cases of CT during pregnancy, but it can be prevented by treatment of the expecting woman with erythromycin. The Danish National Board of Health do recommend screening for CT before transcervical interventions, but there are no such recommendations concerning pregnancy health care. A recent Danish study as well as many other studies have shown that it is cost-effective to screen high risk women i.e. women younger than 25 years. An introduction of such screening of Danish pregnant women younger than 25 years should therefore be considered.