Thermal attack is the basic process that dominates the atmospheric passage of a meteorite. The severity of heating by shocked air (with temperature ranging from 10,000° K to 25,000° K) depends upon pre-atmospheric velocity and angle of entry. It can produce eventually a destructive thermal stress pulse inside the body. While gross fragmentation at higher altitudes seems to have mainly a thermal origin, at lower altitudes the destruction (with occasionally its remarkable abundance of fragments) is likely to be attributed to the combined effect of high temperature and increased pressure. If it is assumed that these conditions control both the number and size distribution of fragments, then much can be learned of the comminution process by studying the fragment distribution in existing meteorite falls.