“This article examines the question of whether there has been a pattern of increasing partisan polarization in decisions by federal judges. After an initial section briefly discussing the general issue of partisan polarization in American politics, the analysis draws on several extant data sources to present evidence of concerning polarization for each of the three levels of the federal courts. That analysis shows increasing, and quite significant, polarization in the behavior of the justices of the Supreme Court, although that is not true for decisions dealing with economics issues and regulation. Much of the change reflects who presidents have been appointing to the Court. For the Court of Appeals and the federal district courts, there is also evidence of increasing differentiation between appointees of the two parties’ presidents. Given the more routine nature of cases below the Supreme Court, the gaps and the change at the lower levels are much less. Again, the nature of the changes varies with the types of cases and those changes significantly reflect who is being appointed to the courts.”