GPOBA is learning more about how to scale-up and mainstream OBA in government programs and operations. This learning process draws from the experience of OBA pilots which help practitioners understand the key prerequisites in considering the usage of OBA in different contexts.   These factors and questions are central to the rationale for having a diagnostic tool as a way to provide guidance to practitioners about OBA feasibility and to encourage the use of OBA as an approach to addressing the basic infrastructure and social services needs of teh poor in developing countries.