Investors’ demand for safe assets tends to increase when there’s more uncertainty, as in recessions. Consistent with this idea, short-term movements in the natural rate of interest, or r-star, are negatively correlated with an index of macroeconomic uncertainty. This relationship may be relevant for assessing monetary policy. An estimated policy rule that incorporates both r-star and the uncertainty index can largely reproduce the path of the federal funds rate since 1988, except during periods when policy was constrained by the zero lower bound.