This article brings a historical perspective to explain the recent dissemination of randomized controlled trials (RCTs) as the new “gold standard” method to assess international development projects. Although the buzz around RCT evaluations dates from the 2000s, we show that what we are witnessing now is a second wave of RCTs, while a first wave began in the 1960s and ended by the early 1980s. Drawing on content analysis of 123 RCTs, participant observation, and secondary sources, we compare the two (...) waves in terms of the participants in the network of expertise required to carry out field experiments and the characteristics of the projects evaluated. The comparison demonstrates that researchers in the second wave were better positioned to navigate the political difficulties caused by randomization. We explain the differences in the expertise network and in the type of projects as the result of concurrent transformations in the fields of development aid and the economics profession. We draw on Andrew Abbott’s concept of “hinges,” as well as on Bourdieu’s concept of “homology” between fields, to argue that the similar positions and parallel struggles conducted by two groups of actors in the two fields served as the basis for a cross-field alliance, in which RCTs could function as a “hinge” linking together the two fields. (shrink)