The prevention of structural collapse during an earthquake having a major intensity at a site is a well recognized objective of seismic design. This project addresses the importance in attaining this objective by ensuring that buildings will not fail while undergoing inelastic response. This research is part of an effort which seeks to provide a practical and reliable methods to check the safety of a building against inelastic dynamic instability. The specific objectives of the research are: a) To investigate the means of identifying the kinematic mechanism that will control a building's dynamic response to sufficiently strong ground motions. b) To calculate instability limits for a number of representative buildings and ground motions using accurate mathematical models. c) To examine the matter of inelastic dynamic instability in the context of code-based seismic design and develop recommended guidelines for design. The development of a method to check instability which accounts for the inelastic dynamic nature of the problem is currently recognized as one of the priority needs for improving seismic design performance standards. This research will lead to a better understanding of how to prevent single story and other undesirable collapse mechanisms.