This paper presents the results of a series of controlled tests conducted with large explosive charges in which a number of threat parameters were systematically varied. After each test, careful measurements were made of the crater dimensions. A statistical analysis was conducted in order to relate the measured crater dimensions to the threat characteristics. The test plan examined the effects of charge size, soil type, shape of the charge, and burial depth. The results of the analysis showed that all of the threat parameters had a significant effect on the most commonly measured dimension, the crater lip diameter. As a consequence, any model that attempts to estimate charge size based solely on crater size measurements will necessarily have large predictive errors, on the order of a factor of two or more.