Noting the difficulties of measuring a company’s export performance and especially financial performance, we develop a new measurement approach grounded on modern portfolio theory. The export intensities and the global financial performance of exporting companies being known, this approach allows deducing the export margin ratio, export risk and correlation of domestic activities with export activities. Using a sampling from French companies in the wine industry from 2001-2005, these implicit financial export performance characteristics are estimated. Main results found: export activities permit a better global margin-risk relationship essentially due to diversification gains because export financial performance seems to be inferior to the domestic one for a great majority of companies.