Partisan polarization in legislators' roll call voting is well established. In this article, we examine whether partisan and ideological differentiation extends to legislators' agendas (i.e., the issue content of the bills and resolutions they introduce and cosponsor). Our analyses, focusing on the 101st-110th Congresses, reveal that differentiation occurs both across and within parties (e.g., Democrats and Republicans tend to pursue different issues in their legislative activity, as do moderate and more ideologically extreme copartisans), but that these differences are not typically large in magnitude and did not increase between the late 1980s and late 2000s. These findings suggest that the dynamics of polarization differ for roll call voting and agenda activities in ways that have important implications for our assessments of its consequences. In particular, they highlight that the polarization that has occurred is less a result of differing priorities between Democrats and Republicans and more a function of different preferences on those priority issues. This differentiation may bubble up in part from the true preferences of the rankand-file, but it is also likely a function of the polarized choices that are presented to them on roll call votes.