The Supplemental Security Income (SSI) program provides an income and health care safety net for the elderly poor. The phenomenon of apparently eligible households that do not enroll in, or ‘take up’ SSI has been noted as a severe problem since the program’s inception in 1974. This paper examines SSI eligibility, applications, and participation in the aged population from 1984 (the most recent year analyzed in the literature to date) through 1997. We are fortunate to have administrative data on SSI use that is linked to various panels of the SIPP. We use this information to estimate the SSI-aged application choice. The key findings from the earlier literature are sensitive with respect to exact sample specification, alternative approaches to imputing the expected SSI benefit, and more detailed information on application and receipt culled from administrative files. Our findings suggest that cash benefits may be less influential, and Medicaid access through SSI more influential, than previously estimated.