European Consortium for Political Research. We would like to thank Matthew Gabel, Simon

We investigate the dimensionality of politics in the European Parliament by applying a scaling method to all roll-call votes between 1979 and 2001 in the European Parliament. Contrary to most existing studies using these methods, we are able to interpret the substantive content of the observed dimensions using exogenous measures of national party policy positions. We find that the main dimension of politics in the EU’s only elected institution is the classic left-right dimension found in domestic politics. A second dimension is also present, although to a lesser extent, which captures government-opposition conflicts as well as party positions on European integration