Recently, Massachusetts passed landmark legislation designed to expand health insurance coverage. This legislation includes a requirement that all adults enroll in a health insurance plan. This mandate takes effect only if an "affordable" plan is available. The definition of affordability for individuals and families of different incomes or circumstances is a critical decision in implementation and is relevant to any state or federal reform requiring individual premium or cost-sharing contributions, or both. This analysis was done to assist the policy design process in Massachusetts and delineates an empirically based approach to setting affordability standards.