In this study, miscibility of blends of poly(vinyl chloride) with poly(ethylene-co-vinyl acetate) (PVC/EVA) have been investigated in tetrahydrofuran (THF) by a viscosimethic method. In order to study the miscibility of the polymer pair in solution, the interaction parameter, Db, obtained from the modified Krigbaum and Wall theory was used. Polymer blends with EVA content of 10%, 20%, 40%, 60% and 80% at a concentration of 6.0 g dm-3 were prepared. Turbidity measurements and the values of the relative viscosities of each of the polymer solutions and their blends were determined. In consequence of the study, it was observed that PVC and EVA miscible each other as limited.