Computation of engineering seismic risk for a project site in the form of “uniform risk” design response spectra is based on the knowledge of total seismicity expected to occur in the project area, where the seismicity is generally defined from the available past data on earthquake occurrence in the area (Gupta, 1991). This paper presents a formulation to evaluate the effect on these spectra of a probabilistic earthquake prediction in the vicinity of the project. A brief review on the strategy of probabilistic prediction using the data on precursory parameters is presented first. Then, assuming a hypothetical but physically plausible earthquake prediction with different reliabilities, example results are computed to illustrate the modifications in the design spectra evaluated for a typical site in northeast India from past earthquake data only. The amplitudes of the design spectra with lower risk levels are found to increase appreciably for higher reliability values of a probabilistic prediction.