Northern Arizona constitutes one of the few remaining unexplored and untested potentially hydrocarbon-productive onshore areas in the contiguous 48 states. The limited drilling exploration to date has proved the presence of oil and gas accumulations near the northeast corner of the state; and, significantly, it has indicated that other large areas have the basic geologic requirements for accumulations. For this review, "Northern Arizona" is considered to be that portion of the Colorado Plateaus province of the state north of the central mountainous region (Fig. 1). For discussion purposes, this portion of the state has been divided into two regions, "northwest" and "northeast." Data have been taken from well and production records of the Arizona Oil and Gas Conservation Commission and from Peirce and others (1970), Peirce and Scurlock (1972), and Scurlock (1973).