The objective of this study was to examine available data on soil response under explosive loading overpressures in the range of interest to the Office of Civil Defense and to apply this information to the foundation conditions at some American cities. Several problem areas were identified which have not previously been considered. These include much larger ground motions than previously predicted when the explosion takes place in water or saturated soil and the possibility of foundation failures due to liquefaction of the supporting subsoil. An examination of the general foundation conditions of six American cities in light of these findings showed that many foundation problems exist which must be taken into account in any shelter design or evaluation program.