Part of the program of the Center for Social Organization of Schools at Johns Hopkins University is one which examines how a student's education affects his actual occupational attainment, and how education results in different vocational outcomes for blacks and whites. This report comes out of such a context. Properties of measures and models of social mobility are analyzed in relation to the conceptualization of mobility. Two main objectives of mobility research are identified. One is the study of determinants of occupational achievement; the other is the study of mobility as a characteristic of social systems. It is shown that the realization of both objectives is hindered by a failure of commonly used models and measures of mobility to separate out the various individual and structural factors responsible for mobility. (Author/JW)