Oil shales of the Eocene Green River Formation in Colorado, Utah and Wyoming constitute the world's largest deposit of hydrocarbons. Tapping of this deposit for commercial production of shale oil appears imminent in Colorado. As a result oil-shale interest oil-shale publicity, and oil-shale land trading have reached impressive proportions. Largely ignored in their stir is Wyoming's oil shale, a resource estimated by Culbertson (1964) to represent 370,000,000,000 barrels of oil in place. Several factors contribute, but the primary reason Wyoming's oil shales receive only token interest is the lack of detailed and valid oil-yield data.