The compatibility behaviour of an epoxidized styrene-butadiene three-arm block copolymer ((ESB)3) with chlorinated polyethylene (CPE) at two degrees of chlorination (36 and 48 wt%) and with poly(vinyl chloride) was investigated over the complete composition range. The techniques used were dynamic mechanical analysis, differential scanning calorimetry and tensile testing. The results were compared with epoxidized block copolymer blends of different architectures, studied before : a linear ESB, a branched E(SB)n and an SBS. The results indicate that miscibility is reduced along the series ESB > (ESB)3 > E(SB)n, at the same level of epoxidation. Additional data on tensile properties on (ESB)3 and E(SB)n blends are also reported. A method is also described to obtain epoxidized semicrystalline poly(hydrocarbons), which when blended with CPE showed a T(m) depression. This allowed the determination of the interaction parameter chi12 of epoxidized poly(hydrocarbon)/chlorinated polymer using the well established method.