The equilibrium defect chemistry of polycrystalline, undoped, and acceptor-doped BaPbO3 was studied by measurement of the equilibrium electrical conductivity as a function of temperature, 800 degrees-900 degrees C, and oxygen activity, 10(-18)-1 atm. Both equilibrium electrical conductivity data of undoped and acceptor-doped samples were quantitatively fit to a defect model involving only doubly ionized oxygen vacancies, lead vacancies, holes, and acceptor impurities. The results in low and midrange of oxygen activity are dominated by acceptor impurities, whether deliberately added or not. Only in the highly oxidized condition is the conductivity independent of impurity content, confirming that this region represents the intrinsic behavior of BaPbO3.