Over the past twenty five years, fiscal and monetary authorities around the world have pursued policies roughly consistent with the insights from optimal monetary and fiscal policy. In the area of monetary policy, the modern consensus is to set policy rules so that nominal interest rates and inflation are low. In the area of fiscal policy, statutory corporate income tax rates have decreased sharply in OECD countries on average over time. Typically, theoretical models in the literature usually examine either monetary or fiscal policies in isolation, but not both of them simultaneously. This book presents two alternative dynamic, general equilibrium models where the prescriptions from optimal monetary and fiscal policies are simultaneously examined. These models offer some new insights on the interaction of such policies, especially in terms of their effects on household's welfare. A third chapter examines optimal fiscal policy in the context of preference reversals. This book should be especially useful for policymakers in the area of macroeconomics and researchers working in the field.