A panel of scientists discussed a variety of issues related to the development of physiologically based pharmacokinetic and pharmacodynamic (PBPK/PD) models for toxicological risk assessment. The panel concluded that although there are a variety of potential technical problems associated with the use of these models for hazard identification and risk assessment, PBPK/PD modeling represents an important technical advance in risk assessment methodology that should continue to be developed and applied. In addition to the technical issues that were addressed, the necessity of providing additional education for toxicologists in the skills necessary for the development and evaluation of PBPK/PD models was stressed.