Recently, there has been a spate of corporate inversions, where U.S. multinational corporations have combined with foreign companies, arranging their corporate structure to locate the residence of the resulting corporation in a foreign country with an attractive corporate tax climate. This paper will discuss both the longstanding features of the U.S. tax system that provide incentives for corporate inversions and the reasons for the present surge in inversions. If unfettered, corporate inversions are likely to undermine the U.S. tax base, so swift policy action is likely warranted. Inversions can be effectively addressed in a targeted fashion.