A series of polymeric blends of semicrystalline sulphonated poly(butylene terephthalate) (SPBT) and amorphous polycarbonate (PC) was studied using small angle neutron scattering. The data has been analysed in terms of Debye-Bueche and two correlation length models. It has been concluded that the blend of unsulphonated PBT/PC is partially miscible, and that temperature, blend composition and particularly sulphonation levels are the principal factors that control its miscibility. The 50/50 blend of 7.9 mol% SPBT/PC is the most miscible at all temperatures studied, and is the most transparent of the blends studied.