The article contributes to a better understanding of implications of scaling up on the social mission of microfinance programs. It proposes a methodology to measure the extent, if any, to which a microfinance program with a poverty alleviation mission drifts away from its mission during rapid scaling up and presents findings from a field research using the proposed methodology at Activists for Social Alternatives (ASA), a microfinance organization that serves poor women in rural India. The findings indicate that mission drift is not a result of deliberate decisions by the management or board but rather is a result of the challenges posed by the scaling-up process. At times, changing trends in social outcomes were not obvious, and management was not aware of the changes indicated by the proposed measures of social performance. (Contains 22 tables and 2 notes.)