The compatibility of melt-mixed blends of poly(ethylene terephthalate) (PET) with two types of poly(ether esters) (PEE) was studied over the complete composition range. The PEE used had a low (PEE-s) or a high (PEE-h) content of hard butylene glycol terephthalate (4GT) sequences. The techniques applied were dynamic mechanical analysis (d.m.a.), d.s.c., tensile testing and optical microscopy. Both blend series showed good tensile properties and this was attributed mainly to the miscibility of the segregated (4GT)(n)-domains in PEE with PET. As the d.m.a. study indicated, miscibility was higher in PET/PEE-h than in PET/PEE-s blends. Depending on blend composition, the PET/PEE-s system showed a wide spectrum of tensile properties spanning thermoplastic, at high PET contents, to self-reinforcing elastomeric behaviour at the other end of the scale of compositions.