Solvent dependent changes in the compatibility behavior of Polychloroprene/Ethylene-propylene-diene terpolymer blends (CR/EPDM) have been investigated using dilute Solution viscometry and solvent permeability analysis. To predict the compatibility of rubber blends of different compositions in solvents of different cohesive energy densities, Huggins interaction parameter (Delta B), hydrodynamic interaction (Delta eta) and Sun's parameter (alpha) were evaluated from the analysis, of the specific and reduced viscosity data of two and three-component polymer solutions. Miscibility criteria were not satisfied for CR/EPDM blends over the entire composition range in toluene xylene, and carbon tetrachloride (CCl4), however, a narrow miscibility domain was observed in chloroform (CHCl3) for CR/PDM/CHCl3 system. These results were further corroborated with the analysis of heat of mixing (Delta H-m) and polymer-polymer interaction parameter (chi(12)) all rubber blend compositions. (C2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 1884-1891, 2009