Since the successful implementations in some prestigious companies such as Motorola, GE & Allied Signal the ¡§Six Sigma¡¨ quality management system has become more and more companies¡¦ priority approach in upgrading their overall competitiveness. With its actual progress made in competitiveness and the shining financial results in the past the Six Sigma has attracted numerous followers and it is now indeed the main quality management stream after the TQM era. No matter the Six Sigma implementation is still under evaluation or has been accepted and ready to kick off, it is no other than one of the main strategic plans of almost all the contemporary companies. However, in spite that Six Sigma has been maturely implemented for some time and there have been some global companies and local companies here in Taiwan that have phased it in already, there are still a lot of local companies that rather wait-and-see and decide not to be the front runners. In Taiwan the number of Six-Sigma companies that have truly phased in and paid off are still quite limited so far. Because of that this research summarized the existing literature based on the key success factors and then validated this hypothesis through expert validation. After the hypothesis was validated, there followed investigations upon the middle and upper level managers who were mostly also students of the NSYSU¡¦s EMBA, MBA (on-job), MBA (night-session), English MBA, MBA (HR, on-job) and ISU¡¦s EMBA and PMBA programs, to have an in-depth understanding on what were theirs and the temporary companies¡¦ wants and anticipated results, what were the differences between their perceptions on the Six Sigma¡¦s key implementation factors, what were the correlations between different independent and dependent variables, and whether there still embedded any tacit factors that could otherwise result in failures. From the result of this research we concluded that no matter what industries and what scales most of the companies have faced with pressure of having to implement Six Sigma. In addition, they believed that Six Sigma truly would be able to help them upgrading their overall competitiveness and corporate images. Also, we learned that there existed differences in independent variables vs. different dependent variables. The perceptions of the middle and upper managements were found not in line with the key success factors in certain degrees in some ways that could otherwise contribute to failures if we do not pay attention to prevent them from happening. Generally speaking, no matter how many employees the companies may have, what capital and revenue sizes they are, all the companies should know of their industries¡¦ own features well for deciding their own directions. They should have appropriate benchmarking and consultants, and need to seek for helps from outside if necessary so that they could take advantage of this new Six Sigma era.