A retrospective study of group B streptococcal endocarditis during 1965-74 in Aberdeen General Hospitals revealed that group B streptococci how principally affect patients in the older age groups with or without a history of antecedent heart disease. Despite recent reports of increased group G infections in obstetric and perinatal practice there were no cases of post-puerperal endocarditis. Although aortic valve involvement would appear to be increasing, group B streptococci still show a marked predilection for the mitral valve.