The paper published by Rose (2000) has cast a new light on the issue of monetary integration. While the traditional approach insisted on the optimality conditions of a currency area, Rose (2000) measures the impact of currency unions on trade. He shows that countries with the same currency trade three times as much with each other as countries with different currencies. In this paper, we intend to re-estimate the impact of currency unions on trade. We underline potential estimation problems and propose a new method of estimation. This paper suggests that the “Rose effect” is not a general result.