Cash transfers to households have become a widely used tool of government policy both as a short-term stimulus during recessions and as ongoing income support to low-income households. This talk discusses the evidence on the aggregate effects of these types of programs. Recent work has found that the household marginal propensity to consume out of temporary transfers is typically lower than previously thought. Moreover, partial and general equilibrium forces, such as responses of relative prices and open economy considerations, further mute the aggregate stimulus effects of temporary transfers. Case studies of prominent transfers suggest very little macroeconomic stimulus. On the other hand, permanent or persistent cash transfers might generate a higher marginal propensity to consume if households are not Ricardian. A question with permanent transfers, though, is the effect on labor supply. Some recent papers have estimated sizeable negative marginal propensities to earn out of unearned income, i.e., households reduce their labor supply in response to rises in unearned income. If this channel is strong enough, persistent cash transfers can depress rather than stimulate the macroeconomy.