The EDITORS have worked together on PBPK research and in teaching PBPK modeling workshops and courses through the Quantitative and Computation Toxicology research group at the Center for Environ-mental Toxicology and Technology (CETT) in the Department of Environmental and Radiological Health Sciences at Colorado State University (CSU).

MICAELA B. REDDY, PhD, is a research professor at CETT where she has developed PBPK models for risk assessment and toxicology applications.

RAYMOND S. H. YANG, PhD, Professor of Toxicology and former director, CETT, championed applications of PBPK modeling in research on the toxicology of chemical mixtures.

HARVEY J. CLEWELL III, MS, Director, Center for Human Health Assessment, CIIT Centers for Health Research, Research Triangle Park, North Carolina, played a major role in the first uses of PBPK modeling in cancer and non-cancer risk assessments by several federal agencies, including EPA, ATSDR, OSHA, and FDA.

MELVIN E. ANDERSEN, PhD, a pioneer in use of PBPK modeling in toxicology and risk assessment, is Director, Computational Biology Division, CIIT Centers for Health Research, Research Triangle Park, North Carolina.