SummaryOur study describes the history of 6 patients with endocarditis, two of them with fatal outcome, caused by nutritionally deficient viridans streptococci, which could only be grown as satellite colonies on blood agar. Supplemented Schaedler broth proved to be superior to supplemented brain heart infusion broth for the isolation of these organisms from the blood. Deficient streptococci were also isolated from the blood of 6 non-endocarditis patients. However, only one blood culture was positive per patient and the isolates were not considered clinically significant.The literature of nutritionally deficient streptococci is briefly reviewed.