**Abstract**

Chlamydial infection is one of the most common sexually transmitted infections worldwide, showing no decreasing trends in the incidence the last years. As a result, it presents a major burden of disease that impacts negatively people's sexual and reproductive health and may result in adverse perinatal outcomes. The aim of the chapter is to offer today's practitioners trustworthy guidance on the latest data in chlamydial infection. Thorough, up-to-date content on the epidemiology, pathophysiology, risk factors, clinical manifestations, diagnosis, treatment, prevention, prognosis and outcomes of infected infants, is presented. Data in children and adolescents that differ from infants, are also discussed. The chapter is organized consistently in order to help readers find information quickly and easily and thus, provide direct, optimal and evidence-based care to every pediatric patient.

**Keywords:** *Chlamydia trachomatis*, chlamydial infection, conjunctivitis, pneumonia, infant, children, adolescents
