The activity of money laundering is a phenomenon integral to the development and mutations of modern societies and defines the effort against organized and non-organized crime to legitimize the money from his actions. The substantial size of those funds usually channeled through multiple transactions in different investment objectives with a view to removing any trace suspect that would refer to the illegal source of origin. The dimension on "money laundering operations in international finance and banking supervision" is centered to the central role played by banks in international economic life and thus the global social and political life. The role of internal audit in banks is particularly important, as it helps each organization to accomplish its objectives by taking a systematic, professional approach to evaluate and improve the effectiveness of the risk, internal control and corporate governance. Management, through internal audit, receives information on the employees' compliance with the procedures, policies and circulars of the Bank. In the first chapter of this study is analyzed the definition of money laundering and the risks posed by Banks. The second chapter, is referring to the statutory framework and in the third chapter are quoted the due diligence obligations of the Banks to the competent authorities. The fourth chapter analyzes the role of internal audit and the fifth presents statistics conducted in a Retail Bank, which we call "Δ" and its Subsidiary "Ω". The standardization of imaging refers to a sample of real data, but the figures in the tables and graphs are estimated from the author of this thesis. Finally, are mentioned the conclusions of the study.