The effects of spall on regional signals are investigated using synthetic seismograms to frequencies of 20 Hz. Depending on the scaling relationships used, it is found that spall may have an important effect on regional body waves and especially surface waves. The frequency range in which the spall effect dominates is dependent upon the characteristic times of the spallation process, but generally occurs in the frequency range of about 0.2 to 2 Hz. Because of the peaked nature of the radiated spall spectra, effects at frequencies outside the 0.2 to 2 Hz frequency range will be dominated by the explosion source. The frequency range and strength of the spall effect depend in a complicated manner upon the yield, depth of burial, near-source structure, and material strength. Uncertainties in the spall scaling relationships need to be better understood before the effects of spall on regional discrimination and yield estimation can be properly quantified. ¿ American Geophysical Union 1989