Temperature dependence of the local structure of relaxor and related ferroelectric oxide systems, such as PMN, PST and PZT, are discussed based upon the results of the pulsed neutron atomic pair‐density function (PDF) analysis. Optical data have shown various changes in the local structure taking place much above the relaxor freezing temperature. However, the origins of such changes have long been controversial. We show that the Burns temperature is the local Curie temperature at which the polar nano‐regions are formed, and the transition is of the order/disorder type for Pb polarization. Local Pb polarization persists up to temperatures several hundreds of degrees above the Burns temperature where the Raman scattering suggests disappearance of the local distortion in the oxygen environment. © 2003 American Institute of Physics