A seismotectonic regionalization of the Great Basin and adjacent parts of the Basin and Range Province, forming six zones, is developed on the basis of generalized late Cenozoic patterns of deformation, relative Holocene strain rates, and historic seismicity. Belts of strike-slip movement are found to be significant in that they separate zones of differing strain rate, style of deformation, and historic seismicity. Within these zones, however, the distribution of historic seismicity may not represent that of Holocene or Quaternary time. Moment rates are computed from both Holocene strain rates and magnitude-frequency parameters of historic seismicity for each of the zones. Although the correlation of these moment rates is quite good the average (geometric) ratio of Holocene to historic moment rates may be about a factor of two. If Holocene aseismic strain release is insignificent, then we might conclude that seismicity in Holocene time is approximately double that of historic time, averaged over the entire Great Basin. Alternatively, it is possible that Holocene strain has been generally overestimated or that much of it has been aseismic.