One of the central tenets of this book is that governmental policies must be designed to take into account market characteristics and environmental phenomena - simultaneously. This volume contains a new research effort of the `Fondazione Eni Enrico Mattei' and explores the theoretical underpinnings of environmental policy in a sub-optimal world. Topics considered link economic issues (oligopolistic market structures, firm heterogeneity, and the strategic behavior of governments) to environmental issues (emission abatements, cleaner technologies, and environmental taxation). The articles in this volume were chosen to achieve a balance between breadth and depth and were written by leading experts in the field. In short, this book is rich in policy implications and raises new issues and questions for future research.