Raman spectra observed for bulk crystals of defect stannite phases in the Cu-(In,Ga)-Se system are analyzed mainly, by the dispersion curve calculations with a superposed lattice model, assuming four fundamental structures. The calculations are performed on the basis of the Keating model, solving dynamical matrix of 24 x 24. Vacancv induced modifications on force interactions between nearest atoms are also discussed with effective bond overlap population and effective charges determined by the DV-Xalpha calculations for unit cell clusters. Apparently, invariable Raman profiles with respect to the In to Ga molar ratios through the alloy systems are explained by the Superposed lattice model. (C) 2002 Elsevier Science B.V. All rights reserved.