The judicial review of legislation can be configured in any of a number of ways. In particular this task may be concentrated in a constitutional court, or diffused among ordinary judges. Recent studies have shown that the design of judicial institutions can have important legal, social, and economic consequences for a given polity. Scholars have dwelled on the reasons that lead political actors to the choice of one model of judicial review over another, but there has been little empirical study on this choice. Here, several hypotheses as to the circumstances that lead to the establishment of constitutional courts are tested on the basis of a data set of 128 democratic constitutions. I find that the degree of political uncertainty facing politicians is an important predictor of whether or not a constitutional court will be established.