Thermal, wide angle X-ray scattering and light microscopy studies have been carried out on sulphonated poly(butylene terephthalate) (SPBT) and its blends with polycarbonate (PC). A better understanding of the morphology and behaviour of the ionomer SPBT as well as initial information on the miscibility and level of crystallinity of the new family of ionomer blends, SPBT/PC, has been obtained. The samples with a degree of sulphonation above 7 mol.% showed the partial miscibility as well as improved optical clarity with respect to blends of non-sulphonated PBT/PC.