Mature museums, in advancing their missions, have often had to reconcile them with some incongruous interests of their most important assets. Staff have often wanted more time to pursue their own interests than employment in a subsidized, public service institution warranted. Large donors have wanted more attention devoted to their particular collection interests than the breadth of the mission would permit. Financial means in general have never measured up to the dreams, and the reconciliation of the ideal with the financially feasible has, as with most endeavours in life, always consumed considerable energy. But it is the interests and forces of the market, the recent arrival of which have benefited museums so much, that are now most to be reckoned with. They can provide almost as much tension with, as support for, the mission, and in the outcome of that tension is many a modern museum’s soul distilled. To understand and manage the mix, we must examine the nature of mission and market strength and how the two relate to each other, in theory and in recent practice.