One-hundred-ninety-three pregnant and seventy five non-pregnant women, aged 18-35 years, were examined for endocervical infection with Chlamydia trachomatis using an enzyme immunoassay technique on cervical specimens. Chlamydia trachomatis was discovered in 7.2% of the pregnant women and in 10.6% of the non-pregnant ones. There was no correlation between chlamydia infection and either previous vulvovaginitis, previous pregnancies or pregnancy outcome. However, younger, more highly educated women with high sexual promiscuity tended to be more frequently colonized.