On 4 November 2002, China and ASEAN signed a Declaration on the Conduct of Parties in the South China Sea (ASEAN, 2002). Incidents related to occupation of islands, ‘illegal’ fishing and oil exploration had been major irritants in the relationship between China, Taiwan, the Philippines, Malaysia and Vietnam during the 1990s. The declaration on a code of conduct reflects the complexity of the South China Sea dispute: it is a multilateral agreement between one major power and an association of ten states. However, China remains adamant that it will resolve the South China Sea dispute only through bilateral negotiations. For this policy to produce results, bilateral talks with Vietnam will be essential. On 25 December 2000, China and Vietnam signed bilateral agreements on maritime delimitation and fishery cooperation in the Gulf of Tonkin, and experts from the two countries also discussed the larger disputes in the South China Sea. However, two years later, the bilateral agreements had still not entered into force and negotiations over supplementary protocols had stalled. This article describes the Sino-Vietnamese rapprochement in the 1990s, analyses the South China Sea ‘irritant’, presents the Gulf of Tonkin agreements and discusses the prospects for a Sino-Vietnamese initiative to resolve the South China Sea dispute.