Two orthogonal joint systems were mapped in the central Alberta plains. These are made up of sets striking approximately 55 and 140 degrees (roughly normal and parallel to the Rocky Mountains) and approximately 5 and 95 degrees. These systems are a continuation of systems mapped in southern Alberta (Babcock 1973). The set orientations persist across lithologic and stratigraphic boundaries. Jointing is attributed to extension fracturing with sets normal and parallel to the Rocky Mountains probably controlled by Laramide orogenic stresses; however, a parallelism between subsurface structural undulations (Robinson et al. 1969) and joints is noted.