Deep source gas research exists to verify that natural gas can exist at depths in excess of 30,000 feet, to relate these occurences to conceptual models, to define the limits of target areas, to quantify the resource, and to determine the potential significance of such finds on the nation's future gas supply. There are three separate emplacement concepts that could explain the occurrence of gas at extreme depths: abiogenic gas; subducted, organic-origin gas; and deep sedimentary basin gas. Of these concepts, deep source gas research focuses on the subducted, organic-origin concept. The research emphasizes an earth science study (geochemistry, and geophysics) of the Cordilleran Geologic Province of western North America. This area is considered a prospective source largely because of known and suspected plate tectonic structures and their youthful emplacement (i.e., during the last 180 million years), which increase the likelihood of a timely entrapment of deep-source generated hydrocarbons. Detailed geochemical studies have indicated that the deep-source, gas-generating capacity of the Aleutian Trench area of southern Alaska may be high (up to 212 trillion cubic feet (Tcf) during the last 20 million years alone). Furthermore, geophysical studies show that an apparent fossil subduction zone exists in western Washington, and this zone appears to have very thick sedimentary rock units. The existence of this zone is being evaluated through detailed seismic studies, and drilling activities may be undertaken in the future. A new technique has helped determine that methane gas can exist at depths up to 40,000 feet. This new technique uses a combination of theoretical computer modeling and laboratory experiments with test rock samples that contain fluid inclusions. 14 refs., 15 figs., 3 tabs.