Combining the topics of rock friction and faulting in one volume is an expression of a certain optimism that information obtained on frictional properties, which comes primarily from relatively small laboratory samples, is relevant to slip on those faults of greatest interest to us, the relatively large ones found in the earth. Probably most workers in this general area believe or hope that this is true, but there is still debate concerning how much progress has been made in relating the laboratory measurements to the earth and how reasonable it is to expect that more progress can be made in the future. The scientific fascination and challenges of these complex topics are enhanced by the possibility they offer for understanding the mechanics of earthquakes that may lead to a workable earthquake prediction program. It is worth reflecting on the similarities and differences between the laboratory and the field settings and on what must be done to understand the mechanics of faulting using laboratory friction data. The articles in this volume are representative of the types of studies that must be combined to attain this goal.