By use of triple-culture tests of each site, Chlamydia trachomatis was isolated from 112 women: from cervical material from 110, urethral material from 32, and rectal material from 19. Triple swabs provided 89 (81%) of 110 diagnoses of cervical infection; the first swab yielded 65 (59%), the second an additional 15 (14%), and the third an additional nine (8%). Three sets of cervical scrapings provided 102 (93%) of 110 diagnoses of cervical infections; the first scrapings yielded 76 (69%), the second an additional 22 (20%), and the third another four (4%). Of 32 women with positive urethral cultures, the first swab was positive in 28 (88%), and the second in the remaining four. Of 19 women with positive rectal cultures, the first swab yielded 11 (58%), the second an additional five (26%), and the third an additional three (16%). The results show that positive culture results obtained by use of a single swab underestimate the prevalence of chlamydial infection.