The dynamical properties of relaxor ferroelectrics have been studied by broadband Brillouin scattering. In 0.65PMN-PT an intense central peak (CP) was observed in a wide temperature range below about 250°C. The relaxation time determined from CP shows slowing down above the cubic to tetragonal transition temperatureTct=158°C.Under the assumption that the origin of CP is the dynamical behavior of polar micro regions, this behavior was well reproduced by the extended superparaelectric model aboveTct.The intense CP of uniaxial relaxor 0.61SBN with the dielectric maximum temperatureTm=70°Cwas also observed in a wide temperature range below aboutTc+400°C.The anisotropy of CP intensity indicates that CP of 0.61SBN is originated mainly from fluctuating polar clusters along the c-axis. However, the slowing down of the relaxation time determined from CP stopped at aboutTm+100°C.This fact may indicate growing interaction between PMRs in 0.61SBN. ©2001 American Institute of Physics.