Many of the largest cities in the United States outsource emergency medical services. This paper develops a political economy model of city service provision. Empirical analysis of emergency ambulances in the 200 largest U.S. cities finds that a number of variables are significant determinants of amblu- ance outsourcing, including the fraction of a city's voters over the age of 65. This finding provides evidence that interest-group politics are important, and suggests a particular shape of the contracting cost curve.