Purpose - Although research has been undertaken on the implementation of lean within various industries, the many tools and techniques that form the tool box, and its integration with Six Sigma (mainly through case studies and action research), there has been little written on the journey towards the integration of the two approaches. This paper aims to examine the integration of lean principles with Six Sigma methodology as a coherent approach to continuous improvement, and provides a conceptual model for their successful integration. Design/methodology/approach - Desk research and a literature review of each separate approach is provided, followed by a view of the literature of the integrated approach. Findings - No standard framework for lean Six Sigma or its implementation exists. A systematic approach needs to be adopted, which optimises systems as a whole, focusing the right strategies in the correct places. Originality/value - This paper contributes to knowledge by providing an insight into the evolution of the lean Six Sigma paradigm. It is suggested that a clear integration of the two approaches must be achieved, with sufficient scientific underpinning.