This Small Business Innovation Research Phase I project will develop an innovative fault-tree-based methodology for dependability analysis of complex computer-based systems. The innovativeness of this approach stems from consideration of multiple failure modes, incorporation of human and environmental influences, adaptation of new techniques from circuit analysis, and using divide and conquer techniques for evaluation of large models. The Phase I objective is to develop an enhanced methodology for dependability analysis of complex computer-based systems. The Phase II objectives are to fully develop and implement a commercializable dependability analysis tool that incorporates the techniques and methods devised in Phase I. The anticipated result of the Phase I effort is the feasibility demonstration indicating that the new methodology will significantly enhance dependability analysis of complex computer-based systems. The benefits include increased effectiveness in this analysis and the potential for more dependable, reliable, and safe systems.