A test of 25 genetically diverse isolates of Bacillus anthracis was conducted to determine their susceptibility to seven clinically relevant antimicrobial agents. Etest strips (AB BIODISK, Solna, Sweden) were used to measure the MICs for the isolates. Using the National Committee for Clinical Laboratory Standards MIC breakpoints for staphylococci, three isolates were found to be resistant to penicillin and five were found to be resistant to cefuroxime. The penicillin-resistant isolates were negative for beta-lactamase production. Continued surveillance of B. anthracis field isolates is recommended to monitor antimicrobial susceptibility.