The Trans-Pacific Partnership (TPP) is a wide-ranging trade initiative that is intended not only to eliminate tariffs but also to offer greater protection for intellectual property and to lower non-tariff trade barriers. The Japanese government’s decision in November 2011 to consider joining the negotiation has dramatically raised U.S. stakes in the deal. And the Tokyo government’s desire to join the TPP talks has sparked a divisive debate in Japan. Japan’s participation in TPP is threatened by still unresolved divisive issues: rice, autos, and the electoral fortunes of the Japanese government. But some Japanese accommodation on autos may be needed if TPP is to get past the U.S. Congress. In the end, whether Japan is in or out of TPP will come down to politics in both Washington and Tokyo.