Why are executive agreements (EAs), rather than treaties, increasingly used to formalize U.S. relations with other countries? We examine this question from two perspectives. In the first, known as the “evasion” hypothesis, presidents act strategically to evade the Senate when governing circumstances are difficult. This strategic view reflects the conventional wisdom. Second, we consider whether organizational efficiency drives presidential use of EAs. As the number of countries increases, requiring more international agreements, it becomes necessary to rely more on an efficient mechanism to “get things done.” We test these rival hypotheses by analyzing EA use as a percentage of all international agreements, as well as a subset of important EAs, from 1949 to 1998. In contrast to the conventional wisdom, we find consistent support for the efficiency hypothesis and only mixed support for the evasion hypothesis. Within these mixed findings, an interesting trend emerges. As expected, presidents act more strategically on the subset of important agreements, but this behavior appears to be driven by the ideological makeup of the Senate rather than partisan cleavages.