A disk potentiation method using carbapenems as substrates and 3-aminophenyl boronic acid as an inhibitor was evaluated for the detection of Klebsiella pneumoniae carbapenemase (KPC)-type beta-lactamases. When combined with nonsusceptibility to ertapenem, the method was easy to perform and reliably differentiated isolates producing KPC-type beta-lactamases from those producing other types of beta-lactamases.