Response Spectrum Analysis (RSA) procedure has become a standard analysis tool in traditional strength-based design of buildings and bridges under reduced seismic loads. RSA has been recently extended to estimate nonlinear seismic demands. The Incremental Response Spectrum Analysis (IRSA) procedure is based on a straightforward implementation of RSA at each piecewise linear incremental step in between the formation of consecutive plastic hinges. The practical version of IRSA works directly with smoothed elastic response spectrum and makes use of the well-known “equal displacement rule” to scale modal displacement increments at each piecewise linear step. IRSA can be characterized as an adaptive multi-mode pushover procedure, in which modal pushover analyses are simultaneously performed for each mode at each incremental step under appropriately scaled modal displacements followed by an application of a modal combination rule. Examples are given to demonstrate the practical implementation of IRSA.