Data were collected on 274 adults to investigate the efficacy of the Supports Intensity Scale (SIS) as a tool to measure the support needs of individuals with intellectual and related developmental disabilities. Findings showed that SIS scores contributed significantly to a model that predicted greater levels of support need. Moreover, scores from different sections of the SIS made unique contributions to explaining variance associated with a variety of support need proxies. Finally, data suggest that the SIS measures a different construct than that measured by traditional assessments of personal competence. The implications of these findings for decision-making, including decisions affecting the disbursement of state developmental disability funding, are discussed.