This paper examines the marginal efficiency cost of various factor taxes in a dynamic general-equilibrium model. The au thor solves for the excess burden of anticipated and unanticipated, t emporary and permanent, tax policies. Using a range of estimates for taste and technology parameters, he finds excess burdens larger than those indicated by previous studies that use static models. These exc ess burdens are sensitive to parameter values and timing. However, th e rankings of alternative tax policies turn out to be insensitive to structural parameter values. Copyright 1987 by University of Chicago Press.