Urogenital Chlamydia trachomatis infection is the most common bacterial sexually transmitted infection in Norway. Urogential C.trachomatis infection can easily be treated with antibiotics. However, left untreated it is a major cause of pelvic inflammatory disease (PID) that can lead to complications such as infertility, ectopic pregnancy and chronic pelvic pain in women. Most infections are asymptomatic and many do not seek the doctor for testing. Therefore cases remain undetected and untreated.We want to determine the efficacy and feasibility of screening for urogenital C. trachomatis infection with home sampling (intervention) compared to the current strategy of conventional sampling at the doctor's office (control) in identifying men and women aged 18-25 years with urogenital C.trachomatis infection (Part A). We also want to identify factors influencing the acceptability of home sampling for C.trachomatis infections (Part B)and determine factors associated with C.trachomatis infections (Part C).