Antimicrobial pharmacodynamics describes the relationship between drug concentration over time, or pharmacokinetics, and treatment outcome. Pharmacodynamic studies provide information useful for dosing interval and dose level selection and for the development of in vitro susceptibility guidelines. Pharmacodynamic observations from animal model studies have proved useful for outcome predictions in treatment of human infections. The strength of these predictions has been shown most clearly for antibacterial drugs. Recent studies suggest that similar analyses may be useful for the clinical development of antifungal drugs.