A study is presented on the use of serological tests for the detection of Chlamydia trachomatis in 273 pregnant women. 166 were cultured for C. trachomatis and nine (5.4%) were positive. Three culture-positive babies, all born to culture-positive women, had conjunctivitis. Elevated IgG and IgA antibody levels were seen in six (67%) and three (33%) of the infected women, respectively. Three (2.4%) of IgG antibody-negative mothers (n = 126) were positive by culture. Compared to serology culture of the microorganism appears as the most reliable way of detecting infected women.