The miscibility behaviour of poly(3-chloropropyl methacrylate) (PCPMA) and poly(2-iodoethyl methacrylate) (PIEMA) with a series of aliphatic polyesters was investigated by differential scanning calorimetry. Binary blends of PCPMA and PIEMA with poly(butylene adipate), poly(2,2-dimethyl-1,3-propylene adipate), poly(epsilon-caprolactone) (PCL) and poly(hexamethylene sebacate) (PHS) exhibit single, composition-dependent glass transition temperatures, characteristic of miscible systems. However, PCPMA and PIEMA are immiscible with poly(ethylene succinate), poly(ethylene adipate) and poly(2,2-dimethyl-1,3-propylene succinate). Blends of PCPMA and PIEMA with poly(2,2-dimethyl-1,3-propylene sebacate) exhibit upper critical solution temperature behaviour. Interaction parameters for PCPMA/PHS, PIEMA/PHS, PCPMA/PCL and PIEMA/PCL blends were evaluated from melting-point depression analysis.