Pediococci, vancomycin-resistant gram-positive cocci, have been isolated from human specimens, but an association with clinical illness has not been established. Clinical and epidemiologic data were obtained on nine patients who had Pediococcus acidilactici isolated from blood. Patients were eight elderly adults with complicated medical problems and one infant with congenital jejunoileal atresia. Seven patients were hospitalized before P. acidilactici was isolated. Eight had received multiple antibiotics; however, only two had received vancomycin. In all cases there was a delay in correct bacterial identification, and the significance of the isolate was uncertain. There was no clearly identified syndrome associated with P. acidilactici bacteremia. All eight adults had fever and six had pneumonia potentially attributable to other causes. The findings underscore the importance of proper identification of vancomycin-resistant gram-positive cocci. P.acidilactici may be an opportunistic pathogen in severely compromised hosts; however, further observations are necessary to clarify its role in human disease.