B-cell peptide epitopes in chlamydial heat shock protein 60 (hsp60) were elucidated with antisera from 13 rabbits immunized with Chlamydia trachomatis serovars B, C, and L2 and antisera from eight women with C. trachomatis-associated ectopic pregnancies. Thirteen major epitopes were identified with the human sera, 10 of which were also observed with rabbit antisera. Seven of the 13 epitopes recognized by human antisera exhibited cross-reactive antibody binding to homologous peptide sequences in human hsp60. Self-reactive B-cell immunity to hsp60 may contribute to chlamydial disease pathogenesis.