The Committee on the History and Heritage of Hydrology sponsored this special session at the 1990 AGU Spring Meeting, held in Baltimore, Md. The history of fracture flow was an appropriate conclusion to 2 days of papers on the geologic characterization of media heterogeneity. Fracture flow theory developed from several technical disciplines, including rock mechanics and geological engineering in addition to hydrogeology. In particular, the 1960s and 1970s saw major advances in methods for describing and analyzing discontinuous geologic features. Institutions such as the University of California, Berkeley, which had strong interdisciplinary groups in the fields mentioned above, spearheaded much of the technical development.