In conjunction with the Tokyo Branch of Japan Association for Maternal Welfare, we have been carrying out examinations of Chlamydial infection on women, especially pregnant women, living in Tokyo. Specimens were collected from 212 gyneco-obstetric clinics in Tokyo during 4 years from January 1987-December 1990. A total of 13,925 swab specimens from patients who were suspected of sexually transmitted diseases from clinical findings and pregnant women who requested the examination were tested for the presence of antigen to C. trachomatis with EIA (Chlamydiazyme). Epidemiological analysis based on the results and case cards that were described sex, age, occupation and clinical findings were conducted. The results obtained are briefly summarized as follows. 1) C. trachomatis antigen was detected in 12.8% (1,237/9,657) of the female patients, 31.0% (124/400) of the male patients and 6.8% (10/168) of the infants. The detection rates of C. trachomatis antigen in the male patients was significantly higher than that in the female and the infants patients. C. trachomatis antigen was detected in 6.1% (226/3,683) of pregnant women. 2) The detection rates of C. trachomatis antigen were compared by occupation of female patients. Most high rate was 26.6% (53/199) in bar hostess , subsequently 20.1% (102/508) in students, 19.8% (59/298) in prostitutes, 13.6% (455/3,348) in office girls and 7.2% (471/6,573) in house-wives. It was noteworthy that the detection rates of C. trachomatis antigen in students was as similarly high as that in prostitutes. 3) The detection rates of C. trachomatis antigen was also compared by age groups. The detection rate had a tendency to be high in younger people.(ABSTRACT TRUNCATED AT 250 WORDS)