The $5.7-billion endowment at Washington University in St. Louis is a nest egg that makes a lot of things possible. Endowment proceeds begat the whimsical, stainless-steel spherical sculpture now hanging in the lobby of the sleek new art museum, which gives off a fun-house mirror effect from below; the sprawling collection of books on the Third Reich that fills more than a room in the library; scholarships for medical students that allow them to graduate with lower levels of debt than the national average; and hundreds of endowed professorships that give deans of the seven schools there the means to reward longtime professors and recruit hot stars from other places. The endowment also underwrites a vast and respected medical-research operation, a $490-million enterprise that, while producing prestige and medical breakthroughs (like a recent finding that links genetic factors to cigarette addiction), costs the university more than $1.20 for every dollar it brings in. Still, to critics in the U.S. Senate and some experts elsewhere, Washington University, along with dozens of other wealthy universities, is far too stingy with its endowment. This article describes how some senators are considering new tax proposals designed to pressure universities to spend more of their assets. The Senate proposal, which has yet to be introduced as legislation, could require rich universities to spend at least 5 percent of their endowment, as private foundations are now required to do, or lose the tax exemption they enjoy on their endowment earnings. (Contains 3 tables and 1 figure.)