The authors describe a case of chronic endocarditis by Q fever, in a patient who had been operated for coarctation of the aorta twelve years previously and at the same time was carrier of a congenital bivalve aorta. The clinical picture was suggestive of subacute endocarditis, but the blood culture was negative repeatedly. There was also a prolonged and relapsing febrile syndrome over a period of one-year-and-a-half. The following data are also worthy of note: the coexistence of a liver disorder and a focal and segmentary glomerulonephritis. Based on some recent publications (one by the same group) the authors feel that Coxiellosis burnetti must be more frequent in their environment than is suspected.