Contributions from the literature on social identity for negotiation theory are discussed in terms of three dimensions of identity. One dimension refers to a dynamic process of negotiating identities. Just as the process of negotiating over divergent interests is influenced by the parties' identities, the identities are shaped by the way that process is conducted. Another dimension refers to the durability of identities, which are shown to have implications for the negotiating flexibility of representatives and their constituents. A third dimension concerns the spread of identities in a population, which are shown to influence the credibility of negotiating commitments, the role played by domestic politics in international negotiation, and the willingness of national representatives to enter into regional or global agreements. These dimensions are used as a framework for comparative research on national identities. Building on Mezran's analysis (article in this issue) of four north African countries, an illustrative application of the framework demonstrates how the research might be implemented.