By its heuristic nature, a study of discontinuity attributes without field data is futile. Thanks to the companies - Haliburton, Geco-Prakla, and Unocal - that supplied migrated image volumes to test the various attribute computations. I especially want to thank Richard Day of Conoco, Kurt Marfurt of Amoco, and Bee Bednar of Bee Consulting for their help in making some of these image volumes available.