The authors report two cases of Bartonella endocarditis in native valves. The first case was a 15 year old North African Girl who lived in poor social conditions and was admitted to hospital with pyrexia and congestive heart failure. Investigations revealed massive mitral regurgitation due to ruptured chordae tendinae, vegetations on the pulmonary valve with severe pulmonary hypertension due to persistent ductus arteriosus. After antibiotic therapy, the patient underwent surgery for mitral valve replacement, pulmonary valvuloplasty and closure of the patent ductus arteriosus. The second case was a 39 year old man with no fixed abode with a history of alcoholism who presented with a recurrent ischaemic stroke in a context of infection with a murmur of aortic regurgitation. Echocardiography showed a vegetation on the aortic valve with grade III/IV regurgitation requiring aortic valve replacement with a homograft after antibiotic therapy. The aetiological diagnosis was made a posteriori by the finding of high antibody titres and specific genetic amplification of Bartonella. In patients with negative blood cultures, Bartonella infection should be looked for systematically especially in those living under poor social conditions. The practical diagnostic investigation of endocarditis with negative blood cultures is reviewed.