Between 450,000 and 650,000 Massachusetts residents are without health insurance. Compared to people with coverage, the uninsured receive less preventive care, are diagnosed at more advanced disease stages, and once diagnosed, tend to receive less therapeutic care and have higher mortality rates. This report estimates the cost of medical care for the uninsured and looks at who provides this uncompensated care. The expansion of coverage would potentially use these resources with new sources of revenue to finance additional care. The more the current spending for uncompensated care could be reallocated, the less the new incremental cost of the coverage expansion. (Roadmap to Coverage, November 16, 2004)