Scholars have pointed to signs of growing polarization in American politics along partisan and ideological lines. This article probes for polarization in the Supreme Court by examining the role of ideological considerations in the selection of law clerks. For the 1975–1998 terms of the Court, we analyzed the relationship between the justices' ideological positions and the positions of the lower court judges from whom the justices drew their clerks. We found that this relationship became stronger over the course of that period, with a sharp increase in strength during the 1990s. This finding provides one significant piece of evidence that the Court has been changing as an institution.