To determine the incidence and the clinical significance of two autoimmune markers in Q-fever (smooth muscle antibodies, cold agglutinins).Six index cases with auto-immune disorders. Assays of 104 sera from patients with Q-fever (including index cases) using immunofluorescence for smooth muscle antibodies, microagglutination for cold agglutinins.French National Reference Center for Rickettsial Diseases.6 patients were studied with acute Q-fever and auto-immune disorders. 3 of whom had presented a resistance to a therapy with antibiotics. Stored samples from other patients with acute or chronic stage were also screened to appreciate the incidence of the two markers.No correlation between Q-fever and smooth muscle antibodies titers and kinetics were found. A spurt of corticosteroids was necessary to obtain apyrexia for the patients who had presented multiple auto-immune disorders and a resistance to the classical therapy. INCIDENCE; Smooth muscle antibodies were detected in 27%, cold agglutinins in one case. They were present in 23% of the patients with acute cases and in 38% with chronic stage.The incidence of auto-immune disorders is unexpectedly high and could explain some manifestations of acute Q-fever e.g the resistance to therapy with antibiotics which are not yet clear. Then the association during the acute stage of auto-immune disorders with the persistence of clinical or biological findings after three weeks therapy could recommend the use of corticosteroids.