During the Workshop Pharmacokinetics: Defining the Dose for Risk Assessment, two panel discussions were held. The first was Design of Studies to Obtain Pharmacokinetic Data for Risk Assessment. Emil Pfitzer of HoffmannLa Roche, Inc.; James Stevens of Ciba-Geigy Corporation;Penelope FennerCrisp of the U.S. Environmental Protection Agency Pesticides Program; and Daniel Menzel of the University of California, Irvine, were lead discussants. The second was How Pharmacokinetics Affects Risk Assessments in Sensitive Populations, Especially the Very Young and the Elderly with Daniel Krewski of the Health and Welfare Canada, John Doull of the University of Kansas, Alan Wilson of Monsanto Company, and Donald Mattison of the University of Pittsburgh as lead discussants. The discussions centered around the