The U.S. Supreme Court has been the focus of much attention by empirical scholars for more than twenty years. The Kelsenian-type constitutional courts have attracted attention more recently. The extent to which constitutional judges respond to party interests has been a matter of theoretical debate that cannot be solved without consistent empirical analysis. In this paper, we discuss the growing empirical evidence on constitutional courts, in particular the cases of Germany, France, Italy, Spain and Portugal. We conclude that party alignment matters, but the patterns of politicization are complex and diverse.