This paper summarizes theories of international migration to identify the economic, political and social forces operating at micro, meso and macro levels of aggregation that account for variation over time in the volume of migrants between contributing and receiving countries. It uses census data and the judgments of historians to establish change over time in the size of the Argentiinan-Jewish and Canadian-Jewish populations; establishes a periodization of Jewish immigration to Argentina and Canada from 1870 to 1920; and shows how different combinations of forces operated in different period to produce unique patterns of ebb and flow in the volume of Jewish immigration in each country. The paper concludes by proposing a general framework for the comparative study of Jewish migrations.