Mobile financial services - often called mobile money - are a high priority for many mobile operators, financial institutions, technology firms, and governments. In regions where financial inclusion is limited, such as sub-Saharan Africa, mobile money promises a lower-cost, more scalable alternative to traditional banking. Yet despite high interest levels in the markets of sub-Saharan Africa, there have been few success stories to date. To cast light on the opportunity, this article attempts to quantify some of the many high-potential payment flows in this rapidly evolving region and to estimate the associated revenue pools.