This paper looks at the use of economic and social 'evidence' in debates on microfinance. Microfinance was originally inspired by small-scale women's savings and credit organisations. When its potential to become a financially sustainable, even profit-making, development intervention was recognised, microfinance underwent a 'revolution' that was to convert it into a much lauded development 'panacea'. Microfinance's reputation has, however, been tarnished by reports refuting the evidential basis for claims made on its behalf. We trace the intervention's ascendance and the evidential basis on which microfinance was promoted. We argue, firstly, that the exclusion of qualitative evidence was not an epistemological imperative, but a political choice, and, secondly, that the large-scale quantitative evidence that did support the scaling up of microfinance was inadequate in terms of methodological rigour. In concluding, we place the example of microfinance within wider debates on evidence in development and argue that evidence can never be apolitical.