The molten salt synthesis (MSS) of lead-based relaxors which have a perovskite structure, A((BBII)-B-I)O-3 where B-I is Mg2+, Fe3+, Zn2+, Ni2+ or Co2+, and B-II is Nb5+, has been reviewed with regard to the formation of the perovskites, phase stability and morphology characteristics. Two relaxer materials, Pb(MS1/3Nb2/3)O-3 and Pb(Fe1/2Nb1/2)O-3 were found to be successfully synthesized at a low temperature in a very short time by the MSS method. Using the example of Pb(Mg1/3Nb2/3)O-3 the Phase stability has been discussed on the basis of thermal and chemical analyses. The influences of the processing parameters, such as temperature, time, type and amount of salt, and non-stoichiometry, on the formation and the powder characteristics of the perovskite phase were investigated with possible explanations for the observed differences which were induced by changing the parameters. Finally, densification behaviour and dielectric properties resulting from the MSS powder were examined and compared to those of powders obtained by using the conventional mixed oxides (CMO) method.