This book attempts to show how technological change is generated and the processes by which improved technologies are introduced into economic activity. This is a far more complex process than it is often made out to be, largely because much of the reasoning and modelling of technological change hopelessly oversimplifies its component parts. The process of technological change takes a wide variety of forms so that propositions that might for instance be accurate when referring to the pharmaceutical industry are likely to be totally inappropriate when applied to the aircraft industry or to computers or forest products. Professor Rosenberg pays particular attention to the nature of the research process out of which new technologies have emerged. A central theme of the book is the idea that technological changes are often "path dependent" in the sense that their form and direction tend to be influenced strongly by the particular sequence of earlier events out of which a new technology has emerged. As a result, attempting to theorize about technologies without taking these factors into account is likely to fail to capture their most essential features. The book advances our understanding of technological change by explicitly recognizing its essential diversity and path-dependent nature. Individual chapters explore the particular features of new technologies in different historical and sectoral contexts.