Four hundred ninety-three women were examined, had a cervical culture done for Chlamydia trachomatis and completed a questionnaire. Sixty-one, or 12.4%, were positive for Chlamydia on culture. Infected women were more likely to be younger, to be unmarried, to have had more sexual partners, to have had past abnormal cytology, to have spotting or postcoital bleeding, to have a mucoid or purulent cervical discharge and to have signs of cervical inflammation, especially friability. No characteristic finding in the past history, symptoms or physical examination combined sufficient sensitivity and specificity to serve by itself as a basis for selective testing for C trachomatis. It appears that multiple characteristics--including history, symptoms, physical examination and cytologic results--must be utilized to select patients for testing.