This paper presents a current, accessible, and overarching view of work system theory. WST is the core of an integrated body of theory that emerged from a long-term research project to develop a systems analysis and design method for business professionals called the work system method (WSM). After discussing WST’s basic premises and its two central frameworks, this paper summarizes the relationship between WST and WSM. It shows how experience with early versions of WSM led to three extensions of WST that addressed limitations-in-use in one of the central frameworks in WST. After comparisons with related theories, this paper closes with an evaluation of progress to date, new directions for research related to WST, and implications for the IS discipline. The two appendices summarize the long term research from which WST emerged and use a positioning map to show how WST is related to other topics in the IS discipline.