Microfinance promises to trim down poverty. To achieve this noble objective microfinance institutions (MFIs) have to become steady profitable because donor constancy is not a given. Thus important question is: what factors drive the financial sustainability of MFIs? Using data on 217 MFIs in 101 countries distributed by region and type of MFIs over the period of 1998-2006, we report three important findings. First, we show that a high quality credit portfolio, coupled with the application of sufficiently high interest rates that allow a reasonable profit and sound management are instrumental to the financial sustainability of MFIs. Second, we show that the percentage of women among the clientele has a weak statistically non-significant negative effect on financial sustainability of MFIs. Third, we find that the client outreach of microfinance programs and the age of MFIs have a positive but lesser impact on attainment of financial sustainability. The policy implication is that MFIs have to emulate profit-making banking practices by implementing a sound financial management and good managerial governance to assure their financial sustainability.