Summary: This testimony discusses growth of the Supplemental Security Income (SSI) rolls and changes in the characteristics of SSI recipients. Last year, the Social Security Administration paid nearly $22 billion in federal benefit payments to about 6.3 million aged, blind, and disabled SSI recipients. Since 1986, payments have risen by $13.5 billion, more than doubling. Benefits for the disabled accounted for nearly 100 percent of this increase. Since 1986, the number of disabled SSI recipients under age 65 has increased an average of more than eight percent annually, adding nearly 2 million younger recipients to the rolls, while the number of aged and blind recipients has remained level. The trend toward younger beneficiaries, coupled with low exit rates from the program, means that costs will continue to burgeon in the near term. Without a slowing in the growth of this younger population, SSI will become even more costly. Since 1991, three groups--disabled children, legal immigrants, and adults with mental problems--have accounted for nearly 90 percent of the SSI caseload growth. Of the two million mentally disabled adults, roughly 100,000 are disabled mainly by drug addiction or alcoholism. The dramatic increases pose fundamental questions about eligibility standards, accountability, and program effectiveness.