An improved method of isolation of Coxiella burnetti proteins was developed. It consists of a combination of detergent (sodium dodecyl sulphate (SDS) or sodium deoxycholate (DOC) and hot phenol treatments. The resulting phenol phase (PP) contained either lipopolysaccharide-(LPS) free proteins (DOC extraction) or proteins contaminated with LPS (SDS extraction), while the water phase (WP) contained LPS. Isolated C. burnetii proteins induced in mice and rabbits antibodies reacting in immunoblot analysis with both phase I and II C. burnetii corpuscles. A rabbit serum against C. burnetii prepared by DOC-phenol extraction did not react with purified I C. burnetii LPS in immunoblot analysis.