Current building codes in the United States provide for five standard ground surface response spectra for seismic design purposes as a function of a site classification based on the weighted average shear wave velocity over the top 30 m of the profile, Vs30, and mapped spectral accelerations at period of 0.2 and 1.0 seconds. These mapped spectral accelerations were obtained using standard ground motion prediction equations and the average shear wave velocity and standard deviation for each site class. The current building codes allow for both the conduct of site-specific seismic hazard analyses and the conduct of site-specific response analyses, but the resulting ground surface response spectra must not fall below 80 percent of the standard response spectra. This paper describes several site conditions which are typical of those sites where it is advantageous to conduct nonlinear site response analyses and argues that there are conditions under which the lower limit is not applicable.