While the Pb containing ferroelectric and antiferroelectric oxides show a large variety in crystal structure, the pulsed neutron atomic pair-distribution function (PDF) studies indicate that their local atomic structures are surprisingly similar to each other. In particular the environment of Pb is nearly independent of composition, with Pb being strongly off-centered in thePbO12cluster, resulting in a large local polarization. A new model is proposed to describe the interplay between the Pb polarization and the random local structural fluctuation. This model explains the relaxor ferroelectricity from a general point of view, while other models such as nano-domain space charge model and the random field model were introduced specifically for hetero-valent systems such asPb(Mg1/3Nb2/3)O3(PMN). ©1998 American Institute of Physics.