Endocarditis by Q fever is a diagnostic and therapeutic challenge given the diagnostic delay and elevated morbidity and mortality it carries. Six cases of endocarditis by Q fever attended over the last 7 years were retrospectively studied. Five patients had been previously diagnosed of valvular involvement and three had prosthesis. Five patients presented a febrile syndrome of prolonged duration with negative hemocultures and progressive valvular changes. One patient presented acute valvular failure requiring emergency surgery. The most significant laboratory data were anemia, thrombocytopenia, high ESR and hypergammaglobulinemia. In the echocardiograms valvular vegetations were observed in 4 cases. All the patients received medical treatment with doxicylin, one associated with rifampicin and another cotrimoxazol. In 4 patients valvular reposition was required due to a severe hemodynamic alteration. After a minimum follow up of 2 years all the patients remain asymptomatic. The serologic evolution is described.