In this article we bring together opposing international relations theories to better understand U.S. foreign policy, in particular foreign trade and aid. Using votes in the U.S. House of Representatives from 1979–2004, we explore different theoretical predictions about preferences for foreign economic policy. We assess the impact of domestic factors, namely political economy and ideological preferences, versus foreign policy pressures. Our three main results highlight the differential effect of these factors in the two issue areas. First, aid preferences are as affected by domestic political economy factors as are trade preferences. Second, trade preferences, but not economic aid ones, are shaped by the president's foreign policy concerns; for economic aid, domestic political economy factors matter more than foreign policy ones. Third, aid preferences are shaped more by ideological factors than are trade ones, but ideology plays a different substantive role in each. Different constituencies support aid and trade. This finding has implications for foreign policy substitutability, "the internationalist coalition" in U.S. foreign policy, "statist" theories of foreign policy, and the connection between public opinion and legislative voting.