The information systems field needs strong cumulative traditions to advance IS theory building and better explain real-world phenomena. Despite the hegemony of theory in our major journals and major improvements in methodology over the years, the field has yet to achieve strong cumulative traditions beyond a few limited areas. In this paper, we propose a methodology for building such traditions by relying on the framework of external validity that Shadish, Cook, and Campbell (2002) suggest. Our methodology classifies accumulated knowledge into four types, highlights several evolutionary pathways for theory building, and explains how researchers can apply it to extend their own theory. To examine the appropriateness of our typology of accumulated knowledge across the IS and management fields, we conducted a literature review of the empirical research in major IS and management journals over a recent two-year period and coded it according to relevant characteristics of Cronbach’s UTOS (i.e., units, treatments, outcomes, and settings). The technology acceptance model, IS success model, and resource-based view literatures illustrate how to apply the methodology. This evidence leads us to believe that establishing a cumulative tradition is well within the IS community’s grasp.