Résumé : The costs and benefits of subsidized microfinance are still controversial. We utilize a cost-function estimation approach that accounts for the double bottom line (social and financial) of microfinance institutions (MFIs) to evaluate how subsidies affect both cost efficiency and risk of mission drift. We control for endogenous self-selection into the business models of credit-only versus credit-plus-deposit. Our results suggest that MFIs that both supply loans and collect deposits need no subsidies to be cost-efficient. In addition, subsidies to these MFIs are associated with an increase in deposit size, which might hurt the most disadvantaged depositors. In sum, combining subsidized funds from donors with deposits increases the risk of mission drift, and can therefore be socially undesirable.