This book contains a collection of the most significant contributions to some of R.M. Goodwin's ideas, which were presented on the occasion of the outstanding economist's 73rd birthday celebrations held in Modena on February 24th, 1986. The most important feature of this book is the unique combination of papers by economists, econometricians and mathematicians. Their papers deal with the different aspects of Goodwin's celebrated models. The book is divided into three parts. The first part contains five papers which describe Goodwin's scientific life. The second part is more quantitative and contains extensions and modifications to the nonlinear model of growth cycles. The third part is an economic reflection linked to Goodwin's themes. The book presents a combination of both qualitative and quantitative contributions to Goodwin's pioneering works.