Chlamydia are intracellular bacteria associated to serious human disease. A vaccine has proved difficult to obtain so far, and current opinions agree that multi-antigen combinations may be required to induce optimal protective responses. In order to identify new potential vaccine candidates, we recently screened the Chlamydia pneumoniae (Cpn) genome and described 53 recombinant proteins which elicited antibodies binding to purified Cpn cells. We now report that six proteins in this group can also induce in vitro neutralizing antibodies. Antibody specificity for the corresponding antigens was assessed by immunoblot analysis of 2DE Cpn protein maps. Furthermore, four of the six in vitro neutralizing antigens (Pmp2, Pmp10, OmpH-like and enolase) could inhibit Cpn dissemination in a hamster model. The results show that these Cpn proteins are immunoaccessible in infectious EBs, and recommend further investigation on their value as vaccine components.