SUMMARY Of 2021 men attending a venereal disease clinic during a 20-month period, 527 (26' 1 07) harboured Chlamydia trachomatis, 310 (15 a 3%) Neisseria gonorrhoeae, and 94 (4' 7%) both organisms. C trachomatis and N gonorrhoeae were isolated in 163 (15' 707o) and 141 (13 -807o) respectively of 1039 women attending the same clinic over a one-year period; 44 (4' 2%) women harboured both organisms.Contact-tracing was carried out for 112 male and 88 female patients infected with chlamydia, none of whom had gonorrhoea. Of the 144 female contacts, 103 (71*5%) attended for examination and 67 (65%) were found to harbour chlamydia. Of the 103 male contacts, 95 (92'2%) attended for examination and 50 (52' 6%) were found to harbour chlamydia. Of the 67 female contacts, about 55% were symptomless as were 5007o of the male contacts. Cultures for N gonorrhoeae from the sexual contacts of patients with genital chlamydial infections showed positive results in 37 (18' 50o) of the 200 contacts examined.For comparison the results of contact-tracing in 201 male and 231 female patients with gonorrhoea were analysed. Of the male and female contacts, 64' 507o and 66 1' o respectively attended the clinic for examination. N gonorrhoeae was isolated from 77' 7%o of the female and from 85' 6%o of the male contacts; about 40% and 5007o respectively were symptomless.The high percentage of symptomless carriers of C trachomatis among sexual contacts emphasises the need for tracing contacts of this infection.

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