Breaking with a long tradition of public financing, European museum institutions experience a drastic increase of the part of their revenues coming from private sector. At the same time, they can invest this money on financial markets through endowment funds. This article proposes to highlight this new way museums have to manage their revenues. In this way, we analyze American museum system where endowment is the rule. This analysis allows us to understand the endowment concept, to grasp their modalities of implementation and financial management and to discuss benefits, but also risks to which European museums expose themselves.