This book investígates the structure and the changes over time of the technological specialization of advanced countries. Innovation is generally regarded as one of the key determinants of national economic performance and competitiveness. During the 1980s much attention was devoted to understanding its dynamics and impact. An increasing amount of studies have been devoted to the aggregate quantity of resources devoted to Science and Technology (S&T). However, less attention has been paid to a systematic analysis of national activities at the sectoral level. One stream of studies has pointed out that technological change is highly diversified across sectors and countries,1 suggesting that the importance of the innovations of each country differ strongly according to their sectoral specialization. We shall here explore the relationship between general tendencies in the S&T system on the one hand and national patterns of sectoral specialization on the other.