What is the effect of Foreign Direct Investment (FDI) on Economic Growth? This book tackles the question at different levels of aggregation: from broad cross-country level analysis to a more detailed firm level investigation. My research reveals three key findings: First, the cross country investigations reveal that less developed countries with a highly skilled workforce have the greatest potential to attain positive growth effects from FDI. Second, the sectoral allocation of FDI matters for economic growth. Third, purely domestic UK firms reap positive spillovers from British multinationals but negative spillovers from foreign multinationals.