This study deals with the process of building up the local congregation and the manner in which missional objectives are achieved. The study is undertaken against the background of the disturbing decline in membership numbers particularly in the two traditional Reformational churches in South Africa, namely the Dutch Reformed Church (DRC) and the Netherdutch Reformed Church of Africa. This decline is in line with similar tendencies in mainstream churches the world over. Collins’s (2006) three questions to the local congregation constitute the point of departure. Firstly: To what degree does the congregation function effectively in line with her mission in the world? Secondly: To what extent does the congregation make a distinct impact on the community? If the congregation were to disappear all of a sudden – will it leave a serious void in the community? The third question deals with sustainability: Is the congregation’s long term impact of such nature that its success is not just attributable to a single leader. The three questions have been adapted according to Collins’s process model (2001) and the key aspects of the theory of building up the local church are discussed in Chapters 2 and 3. The bulk of Chapter 2 deals with the very important matter of the missio Dei and discusses how the congregation should discover and enact her missional calling in the local community. The study furthermore deals with mission in the current South African context, particularly in view of the fact that an entirely new mission field has opened itself up with the influx into the country of so many people from neighboring countries who have come to live in our midst. Chapter 4 deals with the empirical testing associated with the study to establish if the study’s hypothesis, namely whether local churches that have undergone a structured process of building up the local church are missionally more successful than those that have not undergone a structured process, can be verified. The findings in this regard are dealt with in Chapter 5, while certain aspects that characterize the missional congregation in current times are also discussed.