In 1996, a RCOG Study Group reporting on the prevention of pelvic infection highlighted the considerable role <i>C. trachomatis </i>played in female reproductive morbidity and the potential advantages of DNA based assays.  A national screening programme was suggested, as Sweden and the USA had demonstrated that screening women could decrease prevalence and pelvic inflammatory disease rates. In the UK, out with genito-urinary medicine clinics, awareness of the infection and screening was virtually non-existent.  Women attending obstetric and gynaecology-affiliated clinics were at increased risk of ascending infection compared to the general public and ideally placed for opportunistic screening.  However, patients were <i>TESTED </i>only if symptomatic, by specimens taken from the endocervix for culture or antigen detection assay.  It was from this background that the studies commenced.  The thesis comprises of: -  A questionnaire survey assessing sexually active women’s knowledge of <i>C. trachomatis </i>infection and perceived acceptability of different methods and settings for screening.  Women attending induced abortion and family planning clinics in Aberdeen and Leeds were recruited. -  A prevalence study, aiming to identify who should undergo screening.  Sexually active women attending six different clinical settings in Aberdeen’s Obstetrics & Gynaecology department were screened for <i>Chlamydia.</i> -  A study assessing test performance and acceptability of four different screening approaches (enzyme immunoassay of endocervical specimens and ligase chain reaction assay of endocervical, clinician-collected vulva!, and urine specimens) to opportunistically screen pregnant and non-pregnant women, under 25<i> </i>years of age. -  A study evaluating patient-collected vulval swabs, as an alternative to non-invasive screening by urine.  Women under 25 years of age attending a family planning clinic were opportunistically screened and test performance and acceptability evaluated. -  A study determining whether the measurement of chlamydial IgG antibodies alone or in combination with medical history and/or transvaginal ultrasound can predict tubal infertility in subfertile women.