The Crust and Upper Mantle of the Pacific Area contains a special collection of articles based on papers presented at the Symposium on the Upper Mantle Project held at the Pacific Science Congress, Tokyo, August 1966. In order to provide a more comprehensive collection, additional papers were invited from the geophysics section of the Congress. The Symposium was sponsored by the International Upper Mantle Committee; additional papers were selected by a small group appointed by the Upper Mantle Committee. The Upper Mantle Committee was set up jointly by the International Union of Geodesy and Geophysics (IUGG) and the International Union of Geological Sciences to coordinate the Upper Mantle Project, an international program of research on the solid earth sponsored by the International Council of Scientific Unions (ICSU).