The complex perovskite PbMg 0.5 W 0.5 O 3 , exhibiting a long-range B-site cation ordering, has been investigated by Raman scattering from 10 K up to 956 K. The Raman results are systematically treated, and analysed through the characteristic parameters of phonon peaks. The existence of an additional intermediate phase I between the low-temperature antiferroelectric phase A and the high-temperature paraelectric phase P has been demonstrated (T AI 240 K, T IP = 312 K). These results were compared with dielectric measurements. The disappearance of the first-order Raman structures near 1000 K in the paraelectric phase is discussed in terms of dynamic disorder in the Pb and O sublattices.