High-resolution inelastic light scattering was employed to measure the dispersion relationsfor the acoustic excitations in ordered concentrated solutions of poly(styrene)-block-poly(isoprene)copolymers with both symmetric and asymmetric composition and large spacing (220−415 nm). Themorphology is manifested in the rich phonon spectrum recorded for different scattering wave vectors qin the range 0.003−0.034 nm-1. The experimental ωs(q) of the sth branch is directly compared with thetheoretical dispersion from band structure calculations performed for different directions of q in thereciprocal lattice of lamellar and cylindrical periodic structures. The dispersion relations turn out to bea sensitive index of the microphase morphology and the grain orientation.