This paper considers the desirability of the observed tendency of central banks to adjust interest rates only gradually in response to changes in economic conditions. It shows, in the context of a simple model of optimizing private-sector behaviour, that assignment of an interest-rate smoothing objective to the central bank may be desirable, even when reduction of the magnitude of interest-rate changes is not a social objective in itself. This is because a response of policy to "irrelevant" lagged variables may be desirable owing to the way it steers private-sector expectations of future policy. Copyright 2003, Wiley-Blackwell.