Abstract As a foreword to a revision of the paper on this subject prepared early in 1941 a brief review of developments since that time is in order. During 1941–1945 in Alberta chief attention continued, as previously, to center on the southern plains, the east-central plains, and the foothills. One major company was engaged in an intensive exploration program in south-central Saskatchewan and there was some activity in northeastern British Columbia. Inauguration of the Canol project in 1942 brought immediate development of the far north Norman Wells pool, discovered in 1920, and extensive exploration of the Northwest Territories in general. Steady progress was made in application of geophysical methods in Western Canada, especially the seismograph, in both the plains and foothills, and considerable shallow-structure test drilling was done. Surface geological mapping and subsurface studies were widely extended. On the southern plains minor oil pools were discovered at Taber and West Taber in basal Blairmore (Lower Cretaceous) sands and at Conrad in the Ellis (Jurassic) sand. Discoveries of oil in the Princess-Steveville area in basal Blairmore sand and Rundle (Mississippian) limestone were somewhat disappointing, although considerable gas reserves have been indicated. However, the discovery of a small pool of light crude in the Jefferson dolomite of Upper Devonian age at Princess in 1944 was highly significant. The field itself was small, but its effect on geological thinking and as a spur to deeper wildcat drilling to prospect the Devonian formations was most important. Furthermore, it had been demonstrated by this time that