A material parameter Rdis presented, called the “dynamic thermal shock resistance,” which measures the resistance to thermal stress waves induced by very rapid body heating, e.g. by radiation, of both slender and massive bodies. This dynamic parameter is the complementing counterpart to the well-known “quasi-static thermal shock resistance” Rs, which is the classical measure for the resistance to thermal stresses due to temperature gradients induced by ordinary contact (or surface) heating when inertia effects may be neglected. The two material parameters. Rdand Rs, give a very different ranking of materials. Both parameters have an important physical significance: they place a restriction, solely defined in terms of material properties, on the maximum value of the product of a characteristic structural dimension and the specific thermal power or heating.