This paper presents a technique that seems to calculate adequately, from first principles, the mound and cavity growth that occur during nuclear and high-explosive cratering events. The technique features a standard, numerical approach to high-intensity, stress-wave propagation coupled with a unique model of material behaviour in brittle failure. A preshot testing programme is presented which obtains the necessary material properties from logging tests in the medium and from laboratory tests of selected rock samples. In situ properties to be determined by field logging are density and elastic velocity (compressional and shear velocity). Sample properties to be determined by laboratory tests are hydrostatic compressibility (to at least 40 kb), triaxial data, tensile strength, Hugoniot elastic limit, and high-pressure Hugoniot data for the rock near the point of detonation (nuclear only). Calculations are presented for Project Hardhat (5 kt, nuclear in granite), Project Scooter (0·45 kt, high-explosive in alluvium), Project Danny Boy (0·42 kt, nuclear in basalt), Project Sulky (0·09 kt, nuclear in basalt), and three parameter studies featuring rhyolite equations-of-state. The Danny Boy calculation confirmed spalling to be the predominant, nuclear cratering mechanism in hard, dry rock. This observation permitted the construction of a free-fall, throw-out model which gave a reasonable estimate of crater radius and ejecta boundary. The rhyolite parameter studies give some insight into the importance of medium properties in determining crater geometry. Further effort in this area is required; however, the agreement between the above calculations and the field experiments indicates that the technique is capable of resolving this issue.