Edited by R. Michael AlvarezJurisprudential regime theory is a legal explanation of decision-making on the U.S. Supreme Court that asserts that a key precedent in an area of law fundamentally restructures the relationship between case characteristics and the outcomes of future cases. In this article, we offer a multivariate multiple change-point probit model that can be used to endogenously test for the existence of jurisprudential regimes. Unlike the previously employed methods, our model does so by estimating the locations of many possible changepoints along with structural parameters. We estimate the model using Markov chain Monte Carlo methods, and use Bayesian model comparison to determine the number of change-points. Our findings are consistent with jurisprudential regimes in the Establishment Clause and administrative law contexts. We find little support for hypothesized regimes in the areas of free speech and search-and-seizure. The Bayesian multivariate change-point model we propose has broad potential applications to studying structural breaks in either regular or irregular time-series data about political institutions or processes.1 Modeling Decision-Making on the U.S. Supreme Court Supreme Court decisions do two things: they award a judgment, and they provide a rationale for that judgment in the form of a written opinion. The judgment of the case determines who wins and who loses in the legal dispute, and the terms of the victory or defeat. Opinions are important because they provide justifications for the judgment. Those who subscribe to the attitudinal model of judging (Segal and Spaeth 2002)-which asserts that the decisions the Justices reach are due solely to politics-argue that opinions are nothing more than disingenuous post hoc rationalizations of behavior that merely serve to cover up nothing more than unfettered politics.Authors' note: The authors thank Bert Kritzer, Mark Richards, and Jeff Segal for sharing replication data; Jude Hayes and Robert Walker, along with seminar participants at SLAMM 2010, NYU, and USC for helpful comments; Katie Schon, Jee Seon Jeon, and Rachael Hinkle for their research assistance; and the Filomen D'Agostino and Max E. Greenberg Research Fund at NYU School of Law, the Center for Empirical Research in the Law at Washington University, the Wang Xuelian Fund at Tsinghua University, and the National Science Foundation for supporting our research. The editor, R. Michael Alvarez, and two anonymous referees made suggestions that improved the article significantly. For replication data and code, see Pang et al. (2012). Supplementary materials for this article are available on the Political Analysis Web site.Political Analysis (2012) On the other hand, from a legal standpoint, it is hard to believe that opinions are inconsequential (Friedman 2006). To be sure, opinions are justifications, but they also provide legal rules that govern in future disputes. In our common law system, lower court judges rely on the collection of these rules-called precedents-when deciding s...