Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 72.

The study of the Earth's deep interior is the object of a spectacular development due both to new techniques of observation (including very long baseline interferometry and superconducting gravimeters) and to progress in theory spurred by new computing capability. Stimulated by the international SEDI group, founded in 1986, geophysicists from different disciplines—Earth dynamicists, seismologists, geomagneticians, mineral physicists—began to cooperate and integmte more fully one another's work. SEDI meetings favor and promote those close contacts and cooperation. Great efforts will still be needed before all the disciplinary divisions dissolve—if they ever do—but things are clearly improving, as shown by this AGU monograph. We think indeed that this volume is a good, although incomplete, illustration of the situation as described above and that it is a benchmark in the exciting story of the progress in knowledge of the deep interior of our planet.