Using data from the German Socio-Economic Panel (N=6950), this paper analyses equivalent income mobility in West Germany, 1984-93. Four hypotheses, derived from recent North American research and from sociological theory (stratification theory) are tested. They are: 1. that in West Germany, as in the U.S., the poor are a more stable (less mobile) group than the rich; 2. that, as stratification theory predicts, most moves up and down the income distribution are 'short distance' moves; 3. that income polarization (i.e. a declining middle class) has occurred and; 4. that overall income mobility has not increased in the last decade. All but the last hypothesis proved to be false, so the concluding section assesses the implications of these unexpected results for economic and sociological theory.