How many dimensions are there in Congressional roll-call votes? What do dimensions tell us about Congressional politics? Poole and Rosenthal have found one or a very few dimensions. Earlier work has identified problems with Poole and Rosenthal's dimensional fitting method. This paper finds additional problems, showing that when legislators'relative intensity of preferences varies across issues, the Poole and Rosenthal approach will fail. Specifically, while redistributive issues fit their model, distributive and regulative issues allow gains from trade, and thus vote-trading and coalition-building. Roll-call data show voting patterns inconsistent with the Poole and Rosenthal model. Copyright 1994 Blackwell Publishers Ltd..