This paper aims at investigating the relationship between maritime trade and maritime transport costs at sectoral level. The costs and its effect on international trade will be estimated using highly disaggregated data of shipments from five Spanish ports to seventeen destinations. The paper focuses on the effect of maritime networks, services structure and port infrastructure variables on maritime transport costs. The relationship between transport costs and trade is then analysed by applying a gravity model for sectoral imports. We investigate the endogeneity of the trade and transport cost variables by estimating both equations by using instrumental variables methods. The main findings of this study should contribute significantly to explain the variability of maritime transport costs and to quantify the impact of maritime transport costs in maritime trade.