There continues to be considerable confusion and debate regarding the utility of antimicrobial susceptibility testing (AST) to aid in the antimicrobial selection process. With the renewed emphasis on antimicrobial stewardship in both human and veterinary medicine, it is important to consider all disease preventive and diagnostic tools available. The scientific literature is equivocal regarding the correlation between the in vitro susceptibility test result and clinical outcome. These studies also highlight key points that practitioners should consider when using both individual animal AST results and cumulative diagnostic summaries to select antimicrobial therapeutics.