The development of the European internal electricity market is essential for an efficient integration of wind energy into the power system. The deregulation process was firstly characterised mainly by the opening of national markets. Lately, the emergence of supranational, regional power markets adds a truly European dimension by enabling flexible power trade over borders. Requirements for a market design that leads to an economically efficient integration of wind power on a continental scale are currently being investigated within the European TradeWind project. International markets allow the aggregation of widely distributed wind farms into flexible portfolios of supply and demand. Consequently, a good design of international power markets is essential for an efficient integration of wind energy into the power system.