SUMMARY
The main purpose of this study was to investigate the effect of implementing the lean six sigma on organizational performance with the strategic knowledge management as mediating variable in private hospitals in Tehran- Iran. The research method was based on purpose of applied research and in terms of data collection and the analysis method was survey-correlation. The statistical population of this study were 51 private hospitals in Tehran. Questionnaires were used for data collection. Structural equation modeling was used to analyze the data. The results showed that the implementation of the lean six sigma does not have a positive and significant effect on organizational performance; however, it is effective on the strategic knowledge management. On the other hand, strategic knowledge management has a positive and significant effect on organizational performance. Moreover, the implementation of the lean six sigma has a positive effect on the organizational performance through the mediating variable of strategic knowledge management. The research findings can be used to improve the Organizational Performance of Medical centers and private hospitals through the implementation of Lean Six Sigma.