The frequency of genital Chlamydia trachomatis infection in young men in the UK has been found to be consistently lower than that in young women, but studies in such populations might have been affected by selection bias. We tested 798 male military recruits for chlamydia as part of their routine medical examination at Glencorse barracks in Scotland. 78 (9.8%) men were infected with chlamydia; rates of infection were similar in all age-groups. 69 (88%) chlamydia-positive men were asymptomatic. This rate is higher than those usually cited, showing the importance of opportunistic testing for chlamydia in men as well as in women.