The effects of eutectic (BaCuO 2 + CuO) additions and sintering temperature on the morphology, density and critical current of extruded YBCO wires, were investigated systematically over a wide range of temperatures (800–975 °C) and compositions (0–40 mol%). The YBCO-eutectic system was classified morphologically into five distinct regions, which are influenced strongly by the sintering temperature. The main effect of the eutectic dopant is prevention of the sharp drop of critical current, observed in pure YBCO, at sintering temperatures above 920 °C. This effect is facilitated by suppression of exaggerated anisotropic grain growth and the development of visible intergranular cracks in material.