PIP: The migration flow to West Bengal from different parts of the Indian subcontinent is an old phenomenon which can be traced to the beginning of the 19th century when the process of industrialization began in the areas comprising the present West Bengal. As West Bengal gradually industrialized and urbanized, the migration flow which was an equiliberating process up to 1947 turned into a stagnating mechanism in the economic sphere. This paper attempts to treat the causative process generating migration flows into West Bengal. Some popular hypotheses are tested, and their inadequacies in the case of migration in West Bengal are shown. Then a variable incorporating the expected long-run socioeconomic condition of West Bengal vis-a-vis the states/countries belonging to the migration universe of West Bengal was constructed, and this expectational variable appears to have more explanatory power than the observed income differential. Barring the political factor which played the central role in the case of immigration from Bangladesh, the determinants can be ranked in order of importance as 1) linguistic distance, 2) expected socioeconomic condition, and 3) physical distance. The limitation of the framework used is the scaling of linguistic distance and the inability to treat the political variable in a causal matrix of migration.