The authors test several hypotheses about the impact of intergerational class mobility on political party preferences. Test using cross-national data sets representing Britain, the Netherlands, Germany, and the United States over the period 1964-90 suggest a process of acculturation to the class of destination. The authors hypothesized that a class with a high degree of demographic identity influences newcomers more than a class with low demographic identity does and that, the more left-wing inflow there is into a class, the more likely the immobile members are to have left-wing political preferences. The data did not confirm these hypotheses. A macro analysis does, however, show that the level of class voting is weakened by a compositional mobility effect.