Prior to 1995, when the World Trade Organization (WTO) superseded the General Agreement on Tariffs and Trade (GATT), a number of states took advantage of GATT Article XXVI:5(c), which allowed them-as former colonies or component territories of existing GATT members-to quickly and simply join the multilateral trade regime. The speed with which these post-colonial accessions took place, however, varied widely: some states joined immediately upon independence, while others joined much later. Still other post-colonial states passed on this opportunity, only to subsequently begin the longer, more onerous accession process required of other GATT/WTO applicants. Our paper seeks to explain this variation in the timing of post-colonial states' accession to the GATT/WTO. We argue that three key variables explain the timing of accession decisions: 1) a country's trade ties with existing member-states; 2) its existing preferential trade agreement (PTA) commitments; and 3) its domestic political institutions-specifically, the country's level of democracy. Furthermore, we argue that the effects of these variables are conditional upon each other: post-colonial countries with more extensive trade ties to existing member-states were more likely to accede rapidly under Article XXVI:5(c), but only under specific conditions-namely, when they had not already locked in ties with key trading partners through bilateral or regional PTAs, and when they were governed by a more democratic regime. We test this argument empirically using an original dataset of 61 post-colonial states from 1951 to 2004. Our results strongly Rev Int Organ (2012) 7:81-107 support this explanation of GATT/WTO accession and help to clarify the pattern of participation in the multilateral trading system that we have observed over the last half-century.