This paper explores the origins, structure, culture, performance and social agenda of Grameen Bank, a pioneer among microfinance institutions (MFIs). The authors evaluate Grameen's success in implementing founder Mohammed Yunus' vision for sustainable development through microfinance and address competing opinions regarding the MFI's social achievements during the field's brief history. The paper portrays Grameen as a leading force behind the Microcredit Summit Campaign launched in 1997 and the broadening microfinance agenda. After assessing Grameen's record across select financial metrics, the authors conclude that Grameen and MFIs generally have more potential as vehicles for development than as sources of profit. In the opinion of the authors, this development potential presents sufficient grounds to declare that, on balance, Grameen Bank and the microfinance industry it pioneered represent a great success.