This paper discusses a toxicokinetic model describing the distribution of TCDD in the human body during a lifetime. The model divides the body into several physiological compartments, their weights being functions of age. Ingested TCDD is instantaneously distributed over all compartments according to their lipid content. The liver eliminates TCDD from the body by a first-order process. Intake depends on age, as estimated from food consumption survey data combined with data on TCDD concentrations in various foods. It is shown that historical changes in intake, due to changes in environmental concentrations and in dietary habits, should be taken into account as well. Elimination rate and bioavailability, the only unknown parameters in the model, were estimated by calibrating the model to human data on internal concentrations. The generic formulation of the model makes it suitable for slowly eliminated lipophilic compounds in general.