Despite the ongoing worldwide trend toward regional integration, Japan has remained outside of all regional trading agreements. Because more than 60 percent of Japan’s trade is with countries that are members of a major regional bloc, this reluctance may have had significant effects on its pattern and volume of trade. Indeed, the author finds that Japan’s exports have been reduced by the integration of its trading partners, and that this effect has been fairly uniform across integration regimes. The author also finds that regional trading agreements have tended to have a much more negative effect on Japanese trade than on the trade of other nonmembers.