Poly(vinyl phenol) (PVPh) has previously been found to be successful in making immiscible poly(methyl methacrylate) (PMMA)/poly(vinyl acetate) (PVAc) miscible. Poly(ethyl methacrylate) (PEMA) with one more methyl group than PMMA is also immiscible with PVAc. PEMA and PVAc are miscible with PVPh according to the literature. To determine whether PVPh can also cosolubilize PEMA/PVAc, PVPh samples of two different molecular weights have been mixed in this study with PEMA and PVAc to produce a ternary blend. On the basis of the calorimetry data, the ternary PEMA/PVAc/PVPh blend, regardless of the molecular weight of PVPh, has been determined to be miscible. The reason for the observed miscibility is probably that the interactions between PVAc and PVPh are similar in magnitude to those between PEMA and PVPh. A modified Kwei equation based on the binary interaction parameters proposed previously is used to describe the experimental glass-transition temperature of the miscible ternary blend almost quantitatively well. (c) 2006 Wiley Periodicals, Inc.