This study utilized a previously developed computer model, the Shelter Evaluation Program (SEP) code, to investigate the effectiveness of various shelter constructions and occupant postures with regard to resisting the direct effects of a 10 MT surface burst over a range of incident pressure levels. The shelter configurations include wood frame single-story and two-story, load bearing brick wall three-story residental, seven-story brick load bearing wall (warehouse), six-story steel frame curtain wall commercial, and no shelter outside cases. Shelter occupants were considered in two postures; standing and prone. Results indicate that there is a significant reduction in casualties when shelter occupants are in a prone state.