A method for reporting minimum inhibitory concentration (MIC) data that facilitates interpretation by the clinician unfamiliar with clinically achievable drug levels is described. This system uses the inhibitory quotient, which is a number reflecting the multiple of the MIC that would be achieved. Inhibitory quotients are determined for blood, urine, bile, and CSF and reflect achievable drug levels in those body fluids. The use of inhibitory quotients can be extremely helpful to the physician in the rational selection of an appropriate antimicrobial agent.