Abstract. This analysis presents a theoretical approach of the possible costs related to a national economy which desires to be part of a monetary union. The analysis is made in terms of the classical optimum currency areas theory, which represents the basis of the monetary union process. The objective of this theory was to make a monetary union possible. This theory shows that the countries can obtain net benefits as a result of having a common currency, thus being able to avoid the possible adjustment problems. As a matter of fact, its great merit is that it identified certain properties of the countries being part of a monetary union, these properties representing real alternative tools for losing the independence of the monetary policy.

Keywords: the classical optimum currency areas theory; monetary union; asymmetric shocks.