© The several contributors 2008. All rights reserved. Starting from internal market harmonization regulations and with the European Court of Justice's broad interpretation of the Rome Treaty, a common environmental policy have emerged with leader and laggard governments and businesses pulling in opposite directions. Even before the 1987 replacement of unanimity by qualified majority voting, progress was made on product if not process standards. Five phases are distinguished in this chapter: infant (1958-72), adolescent (1972-87), mature (1987-92), sedate (1992- 2005), and selective activism (since 2005). Climate change emerged as a priority policy issue and the EC Commission was active in rescuing the Kyoto protocol. Germany, Denmark, and the Netherlands were the initial environmental leader states, followed by Sweden, Finland, and Austria. The Commission, Environmental Council of Ministers, the European Council, and European Parliament have all been active on climate change as policy entrepreneurs.