This book analyzes the development of the European Parliament's (EP) committees and their relationship with national political parties in the light of the EP's increased legislative role over the last three decades. The book argues that national parties have a greater incentive to care about what goes on in the EP given the growth in its legislative power. Because most of the EP's detailed legislative work takes place in its committees, national parties should be concerned about their involvement with the EP's committee system. Based on extensive original research, this book shows how the EPs committees have changed over time in response to legislative empowerment and analyzes how national parties and individual MEPs use the committee system to further their policy goals. The book makes a theoretical contribution by providing an explanation for the variation in powers of committees between separated and fused systems of government and by adapting theories of legislative organization developed in the context of the US Congress, to the EP. The European Parliament's Committees will be of interest to students and scholars studying the European Parliament, EU institutions, policy-making, and the development of legislatures and political parties.