This reprint of the 1994 volume was produced at the request of the IUGS International Commission on Stratigraphy. The purpose of the 1994 volume was to promote international agreement on principles of stratigraphic classification and to develop an internationally acceptable stratigraphic terminology and rules of stratigraphic procedure. At the time of its first printing, this second edition was the most up-to-date statement of international agreement on concepts and principles of stratigraphic classification and a guide to international stratigraphic terminology. The first edition, published in 1976, was a significant contribution toward international agreement and improvement in communication and understanding among earth scientists worldwide. The revised, second edition updated and expanded the discussions, suggestions, and recommendations of the first edition, expansions necessitated by the growth and progress of stratigraphic ideas and the development of new stratigraphic procedures since release of the first edition.