The sensitivity of culture in Bactec Plus Aerobic/F* culture vials of body fluids from adult patients at a university hospital was compared with that of conventional culture methods, including enrichment in Schaedler broth. Previous antibiotic therapy was recorded at the time of sampling. Analysis of culture results took account of the clinical significance of isolates and impact on therapy. Of 336 specimens evaluated, 81 (24%) yielded positive cultures, of which 50 cultures (15%) were considered to be clinically significant (yielding 71 isolates) and 31 (9%) were considered contaminated. Of the 71 pathogens, 16 (23%) were isolated in the Bactec system only, whereas 13 (18%) grew in conventional media only; 12 of the latter were strict anaerobes. Among clinically significant positive specimens, 19 (38%) were from patients receiving antibiotic therapy. In 27 cases (8% of all specimens and 54% of significantly positive cultures), the isolation of a pathogen led to modification of therapy. Overall, culture in the Bactec system showed higher sensitivity for the isolation of aerobic micro-organisms than Schaedler broth. Most of the difference was due to a better recovery of Streptococcaceae. Additional pathogens found only in resin-containing Bactec media led to 30% of all culture-influenced modifications of empirical therapy. These data confirm that culture of normally sterile body fluids frequently yields results that are useful for guiding therapy. Although more costly than standard enrichment broth, the resin-containing Bactec Plus Aerobic/F* vial can be advantageous for culture of aerobic pathogens from these specimens, particularly in patients receiving antibiotic therapy.