Social Security Disability Insurance (DI) is a vital part of the nation's social safety net, providing essential financial support to millions of disabled workers and their families. Nearly half of beneficiaries rely on the program for the majority of their family income. A fifth receive nearly all of their income from DI. The program is not particularly generous, however, and many beneficiaries face financial hardship. Average family incomes are only about half as large for DI beneficiaries as nonbeneficiaries. Efforts to address Social Security's financing problems should recognize the crucial support that Social Security provides to Americans with disabilities.