As policymakers seek to rein in the nation's escalating health care costs, one area deserving attention is the health system's costly environmental footprint. This study examines data from selected hospitals that have implemented programs to reduce energy use and waste and achieve operating room supply efficiencies. After standardizing metrics across the hospitals studied and generalizing results to hospitals nationwide, the analysis finds that savings achievable through these interventions could exceed $5.4 billion over five years and $15 billion over 10 years. Given the return on investment, the authors recommend that all hospitals adopt such programs and, in cases where capital investments could be financially burdensome, that public funds be used to provide loans or grants, particularly to safety-net hospitals.