The document presents a compilation of measured values for physiological parameters used in pharmacokinetic modeling. The physiological parameters include body weight, tissue volumes, cardiac output distribution, and respiration parameters. Reference values for use in risk assessment are given for each of the physiological parameters based on analyses of valid measurements obtained from the literature and other reliable sources. The proposed reference values are for generic mice and rats without regard to sex or strain. Reference values for humans are without regard to age or sex. Differences between the sexes in mice, rats, and humans are accounted for by scaling the reference parameters within species on the basis of body weight. Reference physiological parameters are for a 0.025 kg mouse, 0.25 kg rat, and a 70 kg man.