Acceleration spectrum intensity (ASI), defined as the integral of the pseudospectral acceleration of a ground motion from 0.1 to 0.5 sec, was originally proposed as a ground-motion intensity measure (IM) relevant for the seismic response of concrete dams over two decades ago. ASI may be a desirable IM in emerging performance-based earthquake engineering frameworks because its consideration of a range of spectral periods makes it useful for concurrent prediction of acceleration and displacement demands in individual structures and also for regional loss estimation where short-period structures are typically prevalent. This article presents a theoretical basis for predicting ASI, based on prediction equations for spectral acceleration, both for individual sites and spatially distributed regions. ASI is found to have a better predictability than conventional ground-motion IMs such as elastic pseudospectral acceleration at a specific period. Furthermore, for site-specific applications conditional response spectra are derived, which can be considered as the correct target response spectra for ground-motion selection, and the features of these conditional spectra as a function of earthquake magnitude, source-to-site distance, and epsilon are examined. For spatially distributed applications, the intraevent correlation of ASI as a function of the separation distance of two sites is derived and compared to that of other common IMs.