A variety of methods have been used to investigate the global trade in illicit antiquities. This chapter will review the main types of methodology used by researchers in this field, and set out some of the findings of each. Using case study examples of specific projects, we will consider the various types of research that have been conducted in this field to date and the current state of knowledge about the relationship between the illicit and the licit sides of the market. We will conclude with a look to the future to make recommendations about productive avenues of research for those who may wish to pursue this kind of enquiry. The antiquities market is a ‘grey market’. This term denotes a mixing in the supply chain of licit and illicit artefacts (Mackenzie and Yates 2017). The latter arise from illegal digging or the removal of objects from above-ground heritage sites in antiquities source countries. These products of looting and theft are often then introduced into the public marketplace, passed off as legitimate through auction sales, or direct approaches of antiquities trafficking intermediaries to dealers or collectors. A tradition of opaque business practices, and the historical lack of focus on forensic provenance documentation and investigation in the market has made it easy for unethical actors to perform this process of inserting illegally obtained and/or unlawfully exported antiquities into the regular supply chain. However, the potential for proper provenance research to aid in the reduction of the illicit trade in antiquities is clear: popular media sources are now regularly covering major provenance research-informed busts of well-known dealers and collectors, and repatriations of significant trafficked cultural objects from dealers, collectors, auction houses, and museums now frequently occur.