The 5S methodology is a very appropriate way to initiate and achieve the process of continuous improvement. This paper studies management practices in successful Japanese companies in order to determine what 5S principles are behind them. After visiting and conducting interviews at five different plants, a multi-case study analysis was developed to identify the key aspects of the success of the implementation of 5S in Japan. Although each of the companies studied is different, there are commonalities that provide for interesting learning. As a result, best managerial practices based on 5S principles are explained, and the most important principles associated with the success of the 5S method are described and discussed.