This book comprises of three separate essays on the role of knowledge on economic growth. The first essay is a multi-country analysis, which investigates the impact of knowledge indicators on economic growth performances of the OECD member countries and the role of knowledge indicators on the catch-up efforts of the follower member countries in OECD. The second essay analyzes the impact of knowledge on the economic growth performance of Turkey and finally the last essay analyzes the impact of knowledge on the productivity of manufacturing firms in Turkey by using firm level panel data. Then according to the results of these studies policy recommendations are introduced at macro, meso and micro levels.