This paper describes cloud-to-ground lightning that lowers positive charge to earth over mountainous terrain in the northern Rocky Mountain region. A sample of 14 visually confirmed ground flashes provided criteria for identifying positive ground flashes by using only measured electric fields. According to these criteria, 75 positive ground flashes occurred within the 2830 km2 sampling area during three consecutive summer seasons. About 3% of all ground flashes lowered positive charge. The area density of positive ground flashes is about 0.01/km2 per summer season compared to an area density of negative ground flashes of 0.3/km2 per summer season. Positive ground flashes occurred within the sampling area on 16 of 48 thunderstorm days. Daily occurrences ranged from 1 to 11. When lightning could be associated with individual thunderstorms, the positive flashes usually occurred in sequence during the final 30 min of the storm. The 75 positive flashes are very similar. Each has a single R stroke followed by a continuing current interval. The continuing current duration distribution is approximately log normal, with range 5 to 160 ms and mean of about 60 ms. The prestroke intervals, the total period of field change preceding the first R stroke, are similarly distributed over the range 65 to 210 ms with mean of about 130 ms. Leader field change durations, the latter portion of the prestroke interval, range from 40 to 70 ms with mean of about 50 ms. The positive ground flashes occurred over mountainous and forested terrain free of man-made structures. Available data indicate that the positive ground flashes for this region may, in most instances, be initiated by positive downward leaders following a horizontally elongated out-of-cloud path to ground.