More and more empirical research in international economics builds on the analysis of bilateral trade flows. Various different international statistical sources are available for researchers and commonly used. Unfortunately, the data happen to differ quite substantially across the different sources with little systematic knowledge on the nature of the differences and their sources as well as the consequences for empirical results. The project aims at providing a thorough analysis of these differences across trade data sources, the timing and geographical location of deviations and will explain the most important reasons for the discrepancies. Finally, econometric analysis on the different data-sets should clarify to which extent deviations across trade data sources influence empirical results and which applications (cross-section or time series evidence) are most affected.