Sixty-three women admitted to the gynecological ward at the University Hospital, Linköping, were studied for the presence of antibodies to Chlamydia trachomatis. 48% of infertile women, 78% of women with ectopic pregnancy and 44% of women with pelvic inflammatory disease had higher titer (greater than or equal to 1:128) IgG/IgA/IgM antibodies to C. trachomatis. Among 55 healthy pregnant women, used as controls, 13% had this high antibody titer. Among 30 women with a titer of greater than or equal to 1:128, 33% of previous conceptions resulted in ectopic pregnancy and 31% resulted in child birth. The corresponding figures among women with no antibodies to C. trachomatis were 12% and 60%, respectively. The prevalence of IgA antibodies varied from 22% to 38% in women with pelvic inflammatory disease, ectopic pregnancy or infertility. The results indicate the importance for C. trachomatis in development of sequelae to lower genital tract infections in women.