Nine strains of satelliting streptococci were recovered from blood cultures of patients with endocarditis, postpartum or postabortal sepsis, or cirrhosis of the liver. Each strain was observed on direct smear of the original blood culture but failed to grow out on subculture to agar media. Successful subculture of these strains was achieved, however, through the use of media supplemented with cysteine, thioglycollate broth, or as satellite growths around a variety of microbial species. Five strains tested for antibiotic susceptibility were found to be uniformly sensitive to ampicillin, cephalothin, chloramphenicol, erythromycin, lincomycin, and vancomycin. Strain variability was observed with penicillin and tetracycline. Based on these observations, we recommend the addition of media containing thiol compounds (i.e., cysteine supplementation or thioglycollate broth) in order to achieve maximal isolation of these streptococci from blood cultures.