Molecular orientation and mechanical properties of miscible poly(styrene)/poly(vinyl methyl ether) (PS/ PVME) blends were compared with those of heterogeneous PS/PVME blends prepared above their temperature of phase separation. The second moment of the orientation function and the Young’s modulus of the heterogeneous systems were found to be higher than those of the corresponding miscible compositions. Furthermore, it was observed that the orientation behaviour of this blend is closely related to the spinodal mechanism of phase separation, in the range of temperatures and compositions investigated. The role of the annealing time and temperature in this process is discussed.