In the modern industrialized and urbanized world, the problem of 'which language user shall have the best opportunity to get which job' has become a key issue in some ethnic conflicts. Language of work, especially of those desirable jobs for which two or more groups compete, greatly influences life-chances of the members of the group. It is because, in an industrial and indsutrializing society, language can be a very strong barrier which blocks the social mobility or advancement of social groups. The present paper is an attempt at the clarification of the causal relationships between the language of work and group conflict for its control. First, a very simple model consisting of a few variables is proposed. Then, through case studies of Slovakia and Bohemia in the late 19th century, Quebec, Kosovo, and Sri Lanka after the Second World War, it is suggested that the incidence and extent of a Ianguage conflict around the lanaguge of work primarily depends upon two factors : the extent of group expectation for disirable job and the amount of supply of such job in which a given language is in normal use.