SummaryWe report a case of endocarditis due toLactobacillus plantarum,occuring on a mitral valve, as a complication of obstructive cardiomyopathy. The route of entrance is maxillary osteitis of a dental origin.Endocarditis due toLactobacillusis a rare infection. Its major characteristic is an occasional resistance to treatment with /j-lactamines. In our case infection recurred in spite of chemotherapy with ampicillin (6 weeks) and gentamicin (14 days). A new treatment with penicillin and gentamicin for 6 weeks resulted in cure. We ascribe the initial therapeutic failure to a moderate sensitivity of the strain to /3-lactamines (M.I.C. 1,25 /ig/ml for penicillin G). We have not observed any tolerance to/5-lactamines.Endocarditis due toLactobacillusshould be treated with a combination of a /Mactamine with an aminoglycoside, in the event of the isolated strain being little sensitive to /3-lactamines.