This article seeks to focus on applications of Geographic Information Systems (GIS) to geologic hazard assessment, as developed in actual consultations in the San Francisco East Bay over the past decade. The applications examined include acquisition of published geologic data onto GIS, fabrication of new products using GIS technologies, combining political concerns and legal restrictions with geohazards into new composite GIS products, and preparation of detailed geohazard maps for earth movement potential. The last areas evaluated are three dimensional storage and retrieval of subsurface geologic information, with emphasis on providing a means to assess ground water resources and expected seismic site response. A number of problems inherent to GIS representations of voluminous geologic data are then discussed in the conclusions, forewarning readers of the many limitations not commonly appreciated by end users of GIS products.