Forty-four intravenous antimicrobials were tested for the presence of (1-->3)-beta-d-glucan (BG). Colistin, ertapenem, cefazolin, trimethoprim-sulfamethoxazole, cefotaxime, cefepime, and ampicillin-sulbactam tested positive for BG at reconstituted-vial concentrations but not when diluted to usual maximum plasma concentrations. False-positive BG assays may occur when some antimicrobials are administered; however, this needs to be confirmed.