The miscibility of poly(hydroxy ether of Bisphenol A) (phenoxy) with poly(2,2-dichloroethyl metfhacrylate-co-methyl methacrylate) (DCEMA-MMA) was studied by differential scanning calorimetry and Fourier-transform infrared spectroscopy. The three binary homopolymer pairs, phenoxy/poly(methyl methacrylate) (PMMA), phenoxy/poly(2,2-dichloroethyl methacrylate) (PDCEMA), and PDCEMA/PMMA, are miscible. However, phenoxy is immiscible with DCEMA-MMA when the MMA content in the copolymer is between 64 and 98 wt%, showing an immiscibility window. Infrared studies showed that phenoxy interacts more strongly with PDCEMA than with PMMA or DCEMA-MMA copolymers.