Chlamydia trachomatis is widely prevalent. It is an obligate intracellular bacterial parasite whose genital strains (genital chlamydiae) are immunologically and epidemiologically distinct from the ocular strains that cause classical trachoma.1 These are transmitted from eye to eye in hot, dry climates, particularly when standards of hygiene are low, but genital chlamydiae are sexually transmitted, and can often be isolated from patients attending venereal disease (VD) clinics in Western countries. Although the conjunctivae may be infected by genital chlamydiae both in neonates, who acquire the infection during parturition, and in adults, through the accidental transfer of infected material to the eye, eye-to-eye infections are rare. Non-specific genital infection?that is, non-gonococcal urethritis (NGU) in men, and the various syndromes in both sexes associated with it?is now a major health problem in Western society.2 The role of genital chlamydiae in the patho genesis of these diseases has now been recognised,3 and the development of sensitive and reliable cell-culture methods for isolating them4-* has led to intensive research into their epi demiology and pathogenicity in the human genlial tract. As a result, groups particularly prone to infection have been identified. This knowledge has produced a dilemma for both the venereologist and the medical microbiologist, partly because the isolation technique, though feasible in specialist centres, is time-consuming and labour-intensive, and therefore unsuitable