Optimum formulations for castables intended for different service conditions are proposed. Silicon carbide castables containing ultradisperse particles of cement, silica fume, and electrofused corundum are developed. The castables do not weaken on heating and display superior operational properties: the compressive strength is 40–80 MPa at sintering temperature 400°C and 50–85 MPa at 1300°C, the strain onset temperature under a load of 0.2 MPa is 1700–1510°C; thermal stability (1300°C — water) is better than 45 heating/cooling cycles (1300°C — water); no change in linear and volume dimensions was observed on heating. The newly-developed castables can find application in various sectors of industry, in particular, as the refractory material for the lining of Whiting furnaces and porcelain kilns.