This paper uses a multicountry macroeconometric model to analyze possible macroeconomic consequences of large future U.S. federal government deficits. The analysis has the advantage of accounting for the endogeneity of the deficit. In the baseline run, which assumes no large tax increases or spending cuts and no bad dollar and stock market shocks, the debt/GDP ratio rises substantially through 2020. The estimates from this run are in line with other estimates. Various experiments off the baseline run are then done. If the dollar depreciates, inflation increases but the effect on the debt/GDP ratio is modest. It does not appear that the United States can inflate its way out of its debt problem. If U.S. stock prices fall, this makes matters worse...