Any tracer in fetal tissue comes from maternal arterial blood. Provided steady state is achieved and intermediate compartments are reversible, the Logan graphical methods should be applicable to the assessment of binding parameters in the fetal brain. Two pregnant rhesus macaques were studied with fallypride and the Logan method was used to assess dopamine receptor distribution volume ratios (DVRs) in both maternal and fetal striatum. The agreement between fetal striatal DVRs using maternal arterial blood and maternal and fetal cerebellum as input functions strongly supports our hypothesis that the conditions necessary for graphical analysis have been met.