For over a century, some economists have pointed out that upswings and down turns in economic activity (along with some key economic variables) seem to follow a surprisingly regular pattern -- a pattern sometimes labeled simply "Kondratieff long waves" in honor of the Russian economist who first rigorously described some of the phenomena leading to these changes. What might to be causes and consequences of these long-term fluctuations? What is the relationship between these so-called long waves and other structural changes, technical revolutions, financial and monetary variables? Finally, if the mechanisms of long waves can be understood, will it be possible to avoid the recurrent recessions in economic development that are as painful for the less developed countries as for the developed ones -- be they socialist or capitalist in orientation? By invitation, an international panel of distinguished scholars met in Weimar, GDR, to discuss these fascinating questions about the existence and nature of long waves. This conference was organized and sponsored jointly by the International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria and the Institute of Theory, History and Organization of Science of the GDR Academy of Sciences, Berlin. A select group of 30 contributions comprise THE LONG-WAVE DEBATE, which thus represents the state of the art in the theory and empirical observation of long-term economic cycles.