The purpose of this book is to inform geoscientists about the progress made in scientific continental deep drilling as a new method for studying the continental crust. The Seeheim symposium was the second meeting organized for experts of the various national programs to present and discuss the results and progress made in their respective programs since the first symposium in Tarrytown in 1984. Various contributors dealt with the present state of - and experience in - deep drilling techniques as well as with the development of logging tools for drilling at high temperatures. Special emphasis was laid on the Continental Deep Drilling Program of the Federal Republic of Germany and its scientific aims.