Considering the impact of transaction costs on trade volumes and prices in Europe, in our thesis, we carried out an overview of the costs of crossing borders and an assessment of the degree of fragmentation of the product market in this world area. Throughout the analysis, we paid attention to the country and/ or industry dimension and at how country- and sector-specific patterns affect the European product market integration process. A special attention is also devoted to the model specifications and estimation techniques. Having discussed extensively the foundations of the gravity equation and the properties of the gravity model with the aim of empirical works in the first chapter of our dissertation, chapter two provides a first assessment of the extent of the integration in Europe by measuring the trade intensity via an augmented gravity equation. The study measures the impact of regional trade agreements (RTAs) on Members’ trade in the European zone and highlights that despite the ongoing enlargement process of its free trade area, the European zone displays rather weak RTAs impacts - in comparison with what one could expect -. The chapter also highlights a number of caveats and difficulties when one wants to accurately measure the extent of trade creation brought about the RTAs in Europe. In particular, the existence of zero observations (non observed commodity flows) between country pairs might have important drawbacks in the estimations. Since disaggregated trade data can be very insightful, chapter three implements such an analysis. Using a gravity-like equation as well, it provides a border effect estimations carried out in a multi-country and multi-sector context. Our findings reveal that remaining technical barriers to trade, market structure and degree of product differentiation play an important role in the explanation of border effects. Furthermore, our results succeed to derive a strongly negative impact of nominal exchange rate volatility on trade, whereas traditional gravity specifications fail to identify this clearly - when regional dummies are introduced-. Hence, chapter two and three provide an overview, via the trade channel, of the degree of integration of the product market in Europe: While European agreements (EAs) in terms of trade are effective, bilateral trade relationships face steady impediments. As expected, intra-EAs trade increases and exports from Member States to non Member States decline. The trade obstacles have many sources. In particular, volatility of the nominal exchange rate is found to have trade-reducing effects. Our results also underscore the interest of using sector disaggregated date since we find that the degree of product differentiation and the market structure enter in the explanation of border effects. Moreover, the various approaches to harmonize the remaining technical barriers to trade on sector desegregation basis were found to act in reducing on the European Union border effect. As for chapter four, it re-visits the issue of price convergence within the EMU. Specifically, we test whether the Law of One Price (LOOP) can be validated over the period 1984-2004. Our results fail to support the LOOP for a large majority of sectors and countries under examination. Furthermore, our findings reveal half-lives of deviation from the LOOP suggesting a price adjustment which is globally less slow that commonly estimated in the literature. Indeed, the EMU is anticipated to affect the behaviour of trading firms that should result in a faster cross-border transmission of price movements across Member States. When attempting to explain the factors at work in the LOOP failure, we highlight that beside the European convergence process, the arbitrage channel explain a non negligible part of the country mean reversion in terms of relative prices. Nevertheless, mixed evidence is found for the impact of cross- country and cross-sector variables.