The miscibility ofbisphenol-A polycarbonate (PC) and poly(styrene-co-methacrylic acid) [P(S-MAA)] was investigated by differential scanning calorimetry (d.s.c.) and dynamic mechanical thermal analysis (d.m.t.a.). They seem to be partially miscible in solution-cast film, but to be immiscible in melt blend. In solution cast blends, they are miscible in a limited range of composition; at fraction of P(S-MAA) > 70 %. Miscibility of the ternary system consisting of PC, P(S-MAA ), and poly(styrene-butyl acrylate) [P(S-BA)] was also examined. The compatibility was enhanced by adding small amounts of P(S-BA) block copolymer.