Offshoring has since long been a matter of concern in developed countries and has recently received growing attention in the economic literature. The aim of this paper is to provide a critical review of definitions of offshoring that have been put forward in recent years, thereby updating the definitions in earlier publications of the Federal Planning Bureau. We also take a closer look at how offshoring can be measured. In the absence of individual firm data, we focus on indirect trade-based measures of offshoring, compare them and present results for Belgium that show an upward trend in offshoring.