Features of the Supplemental Security Income (SSI) program and the social security retirement system interact to create incentives for prospective participants in the aged portion of SSI to withdraw from the labor force and make an early old age insurance (OAI) claim under social security. This paper takes a first close look at this SSI-OAI interaction. The work disincentives posed by SSI rules and the potential interactions between the SSI and social security programs are outlined in a basic theoretical framework. The impact of SSI rules on the financial cost of delaying the initial OAI claim is calculated using earnings records of actual SSI recipients. Regression specifications for early OAI claims that include variables intended to capture the influence of SSI are estimated. Throughout, the analyses are enhanced by access to Social Security Administration records that have been matched to individuals in the Surveys of Income and Program Participation.