The authors propose a definition of time-consistent policy for infinite-horizon economies with competitive private agents. Allocations and policies are defined as functions of the history of past policies. A sustainable equilibrium is a sequence of history-contingent policies and allocations that satisfy certain sequential optimality conditions for the government and for private agents. The authors provide a complete characterization of the sustainable equilibrium outcomes for a variant of Stanley Fischer's model of capital taxation. They also relate their work to recent developments in the theory of repeated games. Copyright 1990 by University of Chicago Press.