The approach used to implement an ERP system is an important decision in its implementation project as it greatly affects the configuration of the system, the allocation of resources and the management of the project and its risks. It will also play a decisive role at all the stages of the ERP system’s life cycle. This chapter discusses the different ways of “going-live” of ERP systems: big-bang, small-bangs and implementation in phases, and describes their advantages and disadvantages. The chapter also presents results of an exploratory study made in 53 Brazilian companies, which implemented SAP R/3. Based on these results, influences of the companies’ characteristics and of the project on the selected method are discussed. The relation of the implementation approach and project time is also presented.