Environmental disputes arise in the process of road construction projects in many areas of Japan. In some cases, these disputes last as long as 10 to 20 years. The sources of the disputes are inevitable value conflicts between the affected groups. The issue is not to reduce the number of disputes but to find ways to resolve them quickly and satisfactorily. The Tokyo Bay Area disputes have been resolved through the system for Settling Environmental Pollution Disputes. Based on case studies, the strong points and shortcomings of the Japanese system are discussed. The analysis emphasizes the importance of the scientific underpinnings of the points at issue. Also, the following points may be concluded: (1) because mediation by the Environmental Dispute Council is held only following the environmental impact statement, it may be called a quasi-judicial procedure; (2) starting mediation late in the planning process has ill effects; and (3) it is difficult for disputants to have confidence in the mediators when they cannot select the mediators themselves. Concrete examples of institutionalized mediation, a system that has been proposed for the United States, are provided. 4 figures, 1 table, and 12 references. (Author abstract modified)