BACKGROUND: Maryland Promoting Readiness of Minors in Supplemental Security Income (PROMISE) model demonstration project has implemented and is evaluating a collaborative, integrated community-based intervention. PROMISE is designed to increase the likelihood that youth who receive Supplemental Security Income (SSI) in Maryland, and their families, will experience better employment outcomes, increased earnings, and decreased public income support. The intervention was conceptualized from extant research identifying factors, which promote competitive integrated employment outcomes for youth with disabilities. OBJECTIVE: In order to effectively assess the impact of the intervention on the participating youth and families it is necessary to ensure that the large-scale statewide project upholds a strong measure of fidelity across implementation sites. That is, does the project deliver the intervention as intended and is it implemented the same way no matter the individual characteristics of the participants and no matter where they live? RESULTS: The authors present a descriptive report on the implementation of Maryland PROMISE, illustrate measures of fidelity achieved in serving 997 transition age youth receiving SSI across the state, show preliminary data on early impact, and offer implications for ongoing PROMISE evaluation and its potential influence on policy and practice.