Published by the American Geophysical Union as part of the Special Publications Series, Volume 1. Since the first edition was published in 1979, the Third International Kimberlite Conference was held in Clermont-Ferrand in 1982. Nevertheless, several of the problems addressed by papers in the first edition of this publication are still valid and remain unanswered today. For example, we still do not understand the spatial and temporal relationship between kimberiite, xenocrysts and xenoliths, nor do we understand why kimberlites occur where they do or why they often intruded ancient cratonic areas periodically throughout geologic time. There is a growing suspicion that continental rifting or perhaps doleritic/basaltic volcanism is a precursor to kimberlitic activity, but the links are tenuous and often conflicting.