The BACTEC 16B resin medium was developed to detect bacteremia in patients receiving antimicrobial therapy. Over a 9-month period, we compared the efficacy of the BACTEC 16B bottle to the conventional aerobic BACTEC 6B bottle. Of a total of 1,524 sets of blood cultures, 79 yielded presumed pathogens. Of these 79 sets, 42 (53.2%) were positive in both the 16B and 6B bottles, 23 (29.1%) were positive only in the 16B bottle, and 14 (17.7%) were positive only in the 6B bottle. For patients receiving antimicrobial drugs, 33 of 34 (97.1%) sets were positive for pathogens in the 16B bottle, but only 15 of 34 (44.1%) were positive in the 6B bottle. In 19 (55.9%) of the 34 sets, only the 16B bottle yielded growth. The resin bottle was more useful for patients with gram-positive bacteremia than for those with gram-negative bacteremia. The BACTEC 16B resin medium increases the recovery of organisms from bacteremic patients receiving antimicrobial agents and should be used in addition to the standard BACTEC aerobic bottle for such patients.