Dumping is one of the most poorly understood and contentious issues in trade policy. The primary reason is that the agreed definitions of dumping are not based on a solid economic foundation. This allows antidumping measures to be used for protectionist ends and to harass trade partners. While putting antidumping measures on a sounder economic foundation in international law may be difficult given their popularity with politicians, no progress can be made until economists provide a theoretically sustainable definition of dumping and devise a set of transparent criteria for determining if dumping is occurring. This paper explains the difficulties with the current definitions of dumping and outlines an agenda for future progress.