Being brittle and having low thermal conductivity, refractories suffer damage and sometimes fail in service as a result of thermal SHOCK. While the approach of those making fine-grained technical ceramics is to make their products sufficiently strong to withstand thermal stresses; the refractory technologist is more cunning. He uses, often little known, devices to provide resistance to thermal SHOCK that minimise but do not eliminate damage to the component. In this paper the basic equations of thermal conduction and elasticity are presented and followed by some immediate results that should guide the designer of components subject to severe thermal environments. The influence of size and shape of the refractory components is then discussed along with ways in which refractory producers can engineer the thermal and mechanical properties. In particular, the methods used to tailor fracture behavior to optimize the thermal SHOCK resistance are treated in some detail.