The aim of this paper is to review the "state of the art" of empirical analysis on the subject of the effects of mergers and acquisitions. After a brief introduction I will present the conflicting evidence outlined, up to the mid eighties, by the Industrial Organization stream of analysis and the Financial Economics one; afterwards, the most important contributions emerged since then, innovative in terms of amount and type of data used and in terms of more accurate methodologies, will be presented. Finally, special attention will be devoted to the still scattered empirical evidence for Italy.

I am very grateful to Laura Rondi and Alessandro Sembenelli for very useful suggestions on an earlier draft; this paper further develops the first chapter of my Ph.D. dissertation in Economics at the University of Rome "Tor Vergata".