A total of 838 women attending a large family planning clinic in Scotland for emergency contraception were offered screening for Chlamydia trachomatis infection. 569 were screened using ligase chain reaction test in first void urine at the time of presenting for emergency contraception and were retested 1 or 2 weeks later. Women aged under 20 and over 30 years were significantly more likely to decline to be tested than women aged 20 to 30. The prevalence of chlamydia was 7.6% in woman aged 24 or less, 5.3% in women aged 25 to 29, and 1.2% in women aged 30 or more. Only two women (< 1%) who tested negative at the time of using EC were positive 1 or 2 weeks later. Women under age 30 who use EC should be offered screening for chlamydia infection and testing at the time they attend for EC is adequate to detect the great majority of infected women.