A genetic classification of Canadian U occurrences is presented, together with lists of elements and minerals characteristic of each type. Of the 11 types listed, 3 are known to be economic in Canada and 2 are potential sources of U; 2 others have proved to be economic in the United States. Th and the rare earth elements are closely associated with U in many types of deposits but are conspicuously lacking in others. U minerals found in each type of deposit are discussed together with other minerals whose spatial distribution is the same as that of U. It is concluded that although the major factor controlling the type of deposit is the genetic process, marked differences in type may also be due to structures in, and type of, host rock. For many deposits there is evidence of more than one period of mineralization; in an extreme case, the original deposit of pitchblende was formed 1.5 X 109 years before the latest period of hypogene mineralization in the same vein.