Theory 125 THE JOURNEY OF LEAN CONSTRUCTION THEORY: REVIEW AND REINTERPRETATION Nelson Biton 1 and Gregory Howell 2 ABSTRACT The theory supporting Lean Construction has been developing since the early 1990s. The result is a set of conceptual foundations, fundamental principles, basic practices and a more or less common vocabulary. These developments challenge the foundations, principles and practices of traditional project management. The lack of a coherent underlying theory of traditional project management in three areas has led to the current problems in the construction industry. Lean Construction is an innovation that was provoked by the inability of traditional practice to solve a set of common and repeating problems on projects. Lean Construction has evolved and developed from Koskela’s seminal work. He proposed a coherent theory that applied concepts and practices from Toyota Production System. This paper traces the journey of Lean Construction theory from its inception by drawing on the work of leading thinkers such as Koskela, Ballard, and Bertelsen and then looks forward to the emerging field of complexity theory and its relationship to projects. The aim here is to explain key developments in theory of Lean Construction and where it is headed. KEYWORDS Lean Construction theory, complex systems, project management, and Cynefin framework. INTRODUCTION "All change, even very large and powerful change, begins when a few people start talking with one another about something they care about."(Margaret Wheatley 2002) Lean construction has been evolving over the last 20 years with theoretical foundations identified in Koskela’s 1992 report. The report captured Lean Construction research agenda of as follows: “Current academic research and teaching in construction engineering and management is founded on an obsolete conceptual and intellectual basis. It is urgent that academic research and education address the challenges posed by the new philosophy. The first task is to explain the new philosophy in the context of construction. Formalization of the scientific foundations of construction management and engineering should be a long-term goal for research.” 1 Nelson Biton, Project Manager, Searlbridge Joint Venture, at Unki Mine, an Anglo American company, Zimbabwe. nelson.biton@gmail.com 2 Lean Construction Institute, United States of America, Ghowell@Leanconstruction.org