This report lays the foundation for determining the gas and oil resources that are realistically available when exploration and production costs, infrasturcture and transportation costs, and environmental impacts are considered. The authors examine four recent traditional assessments of the nation’s potential supply of natural gas and oil resources. They suggest a new methodology: estimating viable resource, which is the gas and oil resource that is available when exploration and production costs, infrastructure and transportation costs, and environmental impacts are considered. This methodology will be used in future research on specific geographic areas. The authors examine four recent traditional assessments of the nation’s potential supply of natural gas and oil resources. The assessments were done by the U.S. Geological Survey National Oil and Gas Resource Assessment Team, the Minerals Management Service, the National Petroleum Council, and the Potential Gas Committee. Although the assessments vary, they each indicate that the Intermountain West contains substantial natural gas and oil resources. Traditional resource assessments, however, are intended to estimate the technically recoverable resource, which does not reflect the amount of resource that can realistically be produced. This report lays the foundation for determining the viable gas and oil resource: that which is available when exploration and production costs, infrastructure and transportation costs, and environmental impacts are considered. The next step in the research will be to apply this methodology to estimate the viable resource in individual geographic areas. The analysis will specify the relationships among gas and oil deposits, technological options, economic costs, infrastructure requirements, environmental impacts, and other variables to allow for a comprehensive assessment of the viable gas and oil resource. (MP)