In this work, the dynamic behavior of poly (methyl methacrylate)/ polystyrene blend to which P(S-0.5-ran- MMA(0.5)) was added was studied. Several blend ( ranging from 5 to 20 wt% of dispersed phase) and copolymer ( up to 20 wt% with respect to dispersed phase) concentrations were studied. The rheological behavior of the blends was compared to Bousmina's (Rheol Acta 38: 73-83, 1999) and Palierne's (Rheol Acta 29:204-214, 1990) generalized models. The relaxation spectra of the blends were also inferred, and the results were analyzed in light of the analysis of Jacobs et al. [J Rheol 43:1495-1509, 1999]. The relaxation spectra of the blends with smaller dispersed phase ( below 10 wt%) and larger copolymer concentrations ( above 0.4 wt%) showed the presence of four relaxation times, two corresponding to the blend phases, tau(F), corresponding to the relaxation of the shape of the dispersed phase of the blend and tb that can be attributed to the relaxation of Marangoni stresses tangential to the interface between the dispersed phase and matrix. The experimental values of tau(F) and tau(beta) were used to infer the interfacial tension (I) and the interfacial complex shear modulus (beta) for the different blends, G decreased with increasing copolymer concentration. beta decreased with increasing blend dispersed phase concentration and decreasing copolymer concentration. The predictions of Palierne's generalized model were found to corroborate the experimental data once the values of tau and beta, found analyzing the relaxation spectra, were used in the calculations. Bousmina's model was found to corroborate the data only for larger dispersed phase concentration.