In order to investigate whether or not Chlamydia trachomatis infection is a risk factor for pregnancy loss, 77 spontaneous abortion patients (6-24 weeks gestation), admitted to gynaecology emergency of Safdarjang Hospital, New Delhi, India. Twenty-five pregnant women (6-16 weeks gestation) attending the same hospital for induced abortion, were included in the study. C. trachomatis antigen was detected in endometrial curretage tissue by enzyme immunoassay (EIA). The detection rate was 15.6% (12/77) among spontaneous abortion patients and 4% (1/25) among women undergoing induced abortion. There was no statistically significant association between the mean age/mean gestational age of those experiencing spontaneous abortion, with and without C. trachomatis infection (26.9 years versus 25.06 years and 11.1 weeks versus 9.6 weeks, respectively). High prevalence of C. trachomatis was found in multigravidae and parous spontaneous abortion patients, compared with that in primigravidae and nulliparous Chlamydia-negative spontaneous aborters (75.0% versus 25.0%; 66.7% versus 33.3%, respectively). The prevalence of chlamydial antigen in patients with no prior history of spontaneous abortion was 16.1% (10/62) compared with 18.1% (2/11) in women with one prior abortion. Further study is required to determine whether C. trachomatis infection is a primary or secondary indicator of risk.