The Koyukon Indians are one of numerous native Alaskan peoples who still pursue a traditionally based hunting, fishing, trapping, and gathering lifeway. They inhabit a broad section of the state's northern interior, a region dominated by boreal forest environments. This subarctic ecosystem provides a relatively sparse array of resources, which are unevenly distributed and highly unstable. Like all foraging peoples, the Koyukon possess a greatly elaborated knowledge of their natural surroundings. Two dimensions of this knowledge are of special importance here: first, it includes an empirical monitoring of ecological dynamics, the processes affecting occurrence and abundance of resources. Second, it incorporates an interpretation of natural history which we would call "supernatural." These environmental perceptions underlie a system for resource management which is a part of traditional Koyukon culture. Knowledge of ecological processes underlies the use of sustained yield principles to govern harvest of resource species. Ideological knowledge includes a well developed conservation ethic and strict prohibitions against over-use and waste. Supernatural punishment follows offenses against the natural world, such as waste of plants or animals. Thus, the Koyukon people combine empirical and supernatural knowledge to create an effective system for long term management of resources.