This paper compares five of the better-known MFI assessment methodologies: ACCION's CAMEL, WOCCU's PEARLS, PlaNet Ratings' GIRAFE, and the methodologies used by MicroRate and M-CRIL. The challenges facing such assessments are then outlined. Assessments of microfinance institutions (MFIs) are essentially performance reviews by independent specialized parties. They provide the basis for peer group benchmarking, and for performance standards: managers can compare their institution's results to the performance of others, or with agreed standards or requirements. Supervisors, funders and networks can use this information to monitor microfinance institutions. Assessments also provide information to potential investors and lenders.