The number and diversity of classifications of rock material, rock mass, and rock structure used in geology and geotechnical engineering are functions not only of the variability of materials, properties, and features involved but also of the uses to which the classifications are to be put [1–4]. Some of these classifications [1–3] are in fact hierarchies of classifications, or classification systems, and are used to assist in arriving at engineering decisions requiring the disciplined consideration of many variables and their interactions. In such cases, perhaps these systems should be given some name other than classification, which connotes to some the processes of ordering and grouping for purposes other than arriving at engineering decisions. It is not the purpose of this symposium to serve as an elimination contest from which one classification will emerge as the winner, enshrined as a unique ASTM standard. The symposium has been organized with the intention that its main outcome will be the publication of at least several classifications, as ASTM standards, each of which will address a well-defined set of engineering needs. The final, full consensus, published standards may or may not closely resemble the methods presented in the following papers. A related purpose of the symposium is to give the rationale underlying each of the classifications. Do the criteria for classifications appear to be sensible? Is this classification really useful? Does one need to classify at all in order to accomplish the objectives to which the classification is said to be addressed?