Most analyses of congressional voting, whether theoretical or empirical, treat all roll-call votes in the same way. We argue that such approaches mask considerable variation in voting behaviour across different types of votes. In examining all roll-call votes in the U.S. House of Representatives from the 93rd to the 110th Congresses (1973–2008), we find that the forces affecting legislators’ voting on procedural and final passage matters have exhibited important changes over time, with differences between these two vote types becoming larger, particularly in recent congresses. These trends have important implications not only on how we study congressional voting behaviour, but also in how we evaluate representation and polarization in the modern Congress.