This paper assesses existing multilateral rules on government procurement from a developing country perspective. It summarizes the economics of discriminatory procurement and investigates to what extent data on procurement reported by members of the WTO Government Procurement Agreement (GPA) reveal changes in sourcing patterns and national purchasing practices over the 1983–92 period. Available data suggest that changes in procurement practices – or the lack thereof – are largely consistent with what theory would predict. Large countries have not been induced to change sourcing patterns, while small countries appear to have become more open. As most developing countries are relatively small in economic terms, this suggests that there may be potentially large welfare gains for developing countries from accession to the GPA.