Time elapses continuously not in discrete jumps of, say, a quarter or a month. Hence models specified in continuous time are more realistic than the usual models in which time is taken to elapse in such discrete jumps. However much data available to economists is of the discrete-time kind. This was once thought to render impossible the econometric estimation of continuous time models. Over the past decade a body of theory has been built up to show that such estimation is not only possible but has serious practical applications. This collection of essays aims to provide not only the latest developments in the theory but also with original examples to show how it is possible to implement in real situations. Econometricians may find this book useful reading as may those concerned with macroeconomic issues who wish to keep in touch with the "frontiers" of their subject.