This paper is to determine factors best describing a microfinance institution’s (MFI’s) operational selfsufficiency (OSS). The OSS is defined as the ratio of an MFI’s operating revenues to it operating expenses including the financial costs and impairment losses on loans. The outreach of an MFI, the writeoff ratio and regional differences are found significant in determining the OSS of MFIs. Surprisingly, neither an MFI’s depositors-to-borrowers ratio nor its deposits-to-loan portfolio ratio was found to be significant to explain an MFI’s OSS. There was no significant difference in the OSS in 2006 - before the worldwide financial crisis - and in 2008
