While the WTO now represents most of the world's population, GDP, and trade, the accession process since its founding has been lengthy, and it is getting longer. Compared to its predecessor, the GATT, the WTO applies a much more detailed and legalistic approach to accession, due to its broader scope of policy coverage and the enforcement powers of the Dispute Settlement Understanding. In WTO accession cases, WTO incumbent members have a superior bargaining position. The present study provides evidence that the elapsed time from WTO application to accession has increased with the number of completed accessions, suggesting a process of learning by WTO members to bargain for more demanding concessions from applicants. Regarding the terms of accession, the number of rules commitments has increased, and the level of bound tariffs has fallen, as the number of completed accessions has increased. In view of the difficult cases remaining in order to complete universal WTO membership, the author proposes more flexibility in accession requirements, along the lines of the GATT tradition.