The basic philosophy of the National Park Service is to establish "pleasuring grounds" for the "enjoyment of the people." They are also charged with preserving ecosystems and wildlife and maintaining the remnants of our wilderness past. No one animal represents the conflict of these interests better than the grizzly bear (Ursus horribilis). This animal is the most dangerous predator in the Yellowstone ecosystem, yet the very nature of the national park system puts these magnificent beasts in regular contact with human beings. Predicting the potential of interaction between the grizzly and man would be of great value to the park service and the public at large. During the latter portion of the summer, a large part of the grizzly's diet consists largely of army cutworm moths and the caterpillars that precede them. If you can predict the habitat of these moths and caterpillars, you can predict the areas to which grizzly bears will migrate in the latter portion of July and August, prime tourist months for the park. Using a rule-based approach for developing high probability moth habitat areas, this paper will develop likely areas of moth and hence bear habitat. These GIS databases will be overlaid on various human activity maps utilizing evaluation tools in ArcInfo to predict potential areas of human/grizzly interaction. These predictions will be validated using grizzly sightings during the time period in question.