Abstract: This short technical report provides an empirical analysis of the level of institutional block ownership overall, and of foreign block ownership, at a broad set of publicly traded corporations. Disclosed institutional blockholders of every company in the Standard & Poor’s 500 index are analyzed, and the distribution of blockholders is presented. Blockholders are identified as domestic or foreign entities, and whether they were majority owned or controlled by foreign entities. Roughly one in three companies in the S&P 500 has one or more block holders with 20 % ownership, and one in eleven (9%) has one or more foreign institutions each owning five percent or more blocks of stock. The descriptive data reported here may assist lawmakers, analysts, and investors in assessing the effects of globalization of capital markets and the interaction of country and governance risk, and in developing policies. Among other things, these data may inform debates on the degree to which domestic political spending by U.S. corporations conveys any potential for foreign influence through governance, and the likely costs and benefits of disclosure laws regarding such influence.