The path of new compounds from discovery to bedside is long and costly and a large majority of compounds never make it to the market. To improve drug development, better tools are needed to assess efficacy and safety early in the process. One approach that has been suggested by the FDA to help streamlining the drug development process is pharmacokinetic/pharmacodynamic (PK/PD) modeling and simulation. In this approach, a model-based link between PK profiles and corresponding PD is established. Once a suitable model is identified and validated, predictions about efficacy and safety of different dosing regimens can be made. The goal of this review is to examine the current state of PK, PD, and PK/PD in antibiotic and antiviral research and development.