This paper develops the quantitative implications of optimal fiscal policy in a business cycle model. In a stationary equilibrium, the ex ante tax rate on capital income is approximately zero. There is an equivalence class of ex post capital income tax rates and bond policies that support a given allocation. Within this class, the optimal ex post capital tax rates can range from close to independently and identically distributed to close to a random walk. The tax rate on labor income fluctuates very little and inherits the persistence properties of the exogenous shocks; thus there is no presumption that optimal labor tax rates follow a random walk. Most of the welfare gains realized by switching from a tax system like that of the United States to the Ramsey system come from an initial period of high taxation on capital income.