Surface studies of fractures, on both local and regional compressional structure, show a definite relation between the trend of the fractures, their density, and the structure on which they occur. The susceptibility of any stratum to fracturing is dominantly controlled by the thickness and lithologic character of the stratum. These factors are evaluated and used to convert fracture data taken on beds of various lithologic character and thickness to a datum bed. Fracture-pattern and iso-fracture maps are then constructed from these data. These methods were applied in the field to 2 areas in Wyoming: the Goose Egg dome of local extent, and the Sheep Mountain area, of regional extent. These areas show that the trend and concentration of fractures are controlled by the compressional structure configuration.