Infection with Chlamydia trachomatis accounts for the most common bacterial sexually transmitted infection in the UK. Men between 20 and 24 years and women between 16 and 19 years have the highest prevalence of chlamydial infection. Because the majority of women with chlamydial infection are asymptomatic, a proportion remains untreated and eventually develops pelvic inflammatory disease (PID). PID can result in ectopic pregnancy, infertility and chronic pelvic pain. Screening for chlamydial infection might reduce the incidence of complications of PID. The advent of nucleic acid amplification tests and single-dose therapy for chlamydial infection has made home testing and easy treatment possible.