The authors describe important trade-offs that microfinance practitioners, donors, and regulators navigate. Drawing evidence from large, global surveys of microfinance institutions, they find a basic tension between meeting social goals and maximizing financial performance.  Potential trade-offs therefore arise when selecting contracting mechanisms, level of commercialization, rigor of regulation, and the extent of competition. Meaningful interventions in microfinance will require making deliberate choices – and thus embracing and weighing tradeoffs carefully.