The Massachusetts 2006 health care reform has been called a model for the Affordable Care Act. The law attained near-universal insurance coverage and increased access to care. Its effect on population health is less clear. This study compares mortality rates before and after reform in Massachusetts versus a control group with similar demographics and economic conditions. The results show that reform in Massachusetts was associated with a significant decrease in all-cause mortality and mortality for conditions amenable as compared with the control group. Changes were larger in counties with lower household incomes and higher pre-reform uninsured rates.