Physiologically based pharmacokinetic (PBPK) modelling has been used to examine the relative importance of physiological differences between laying hens and broiler chickens as well as between broiler chickens and ducks, geese, and turkeys in determining tissue residues. Following exposure in feed, there may be significant differences in tissue residues between laying hens and broiler chickens. The blood lipid content of laying versus broilers, the duration of exposure, and the fraction of the dose absorbed into the systemic circulation were important parameters together with tissue-to-blood partition coefficients. The potential for modelling to improve the extrapolation of residue transfer studies carried out using laying hens to broiler chickens and other poultry is demonstrated.