Pre-print, Working paper: The purpose of this paper is double. First, we empirically explore to what extent the determinants of trade in services differs from those of trade in goods and, second, by the use of instrumental variables, we explore for potential complementarities between bilateral trade in goods and bilateral trade in services. By the use of gravity equations, the main results show that "bilateral trust and contract enforcement environment", "networks", "labor markets" and "technology and technology of communication" have higher impact on service trade than on trade in goods; finally, after instrumenting for endogeneity, we found that bilateral trade in goods explains bilateral trade in services: the resulting estimated elasticity is close to 1. Reciprocally, though to a lesser extent, bilateral trade in services affects positively bilateral trade in goods: a 10% increase in trade in services raises traded goods by 4.6%.