The association between humoral immunity to unique and conserved epitopes of the Chlamydia trachomatis 60-kDa heat-shock protein (hsp60) and immunity to human hsp60 was examined in 129 women with laparoscopically verified pelvic inflammatory disease. An ELISA was used to detect antichlamydial IgG and IgA antibodies, IgG antibodies to recombinant human hsp60, and antibodies to two synthetic peptides of chlamydial hsp60. Half of the patients had antibodies to human hsp60, which correlated with the presence of antibodies to the chlamydial hsp60 peptide 260-271 homologous to the human hsp60 (P = .01). Antibodies to peptide 260-271 were associated with antichlamydial IgG (P < .0001) and IgA (P < .0001). The results suggest that the autoimmune response to human hsp60 can develop following C. trachomatis upper genital tract infection in women, probably as a consequence of an immune response to an epitope of chlamydial hsp60 cross-reactive with the human hsp60.