ABSTRACT Cigarette smoking is the leading cause of preventable death in the United States. Despite a substantial decrease in cigarette smoking over the past decade, cigarette smoking accounts for nearly half a million deaths nationally, more than alcohol and illicit drug use combined. People living with intellectual and developmental disabilities (IDDs) are exceptionally vulnerable to dangers posed by cigarette smoking because it may worsen health conditions common among people with IDDs, including diabetes and asthma. People living with IDDs are at an increased risk of developing a tobacco use disorder (TUD), have a lower likelihood of entering treatment and have a higher probability of dropping out of treatment. These issues highlight serious health equity concerns for people with IDDs, including stigma, exclusion, underrepresentation, and lack of access to high quality care, and may contribute to both the onset of cigarette smoking and serve as barriers to tobacco treatment enrollment, thus making people with IDDs vulnerable to persistent TUD and tobacco-related disease. The goal of this K99/R00 Pathway to Independence Award is to use a community engaged approach to elucidate treatment difficulties in IDD populations and use the information gained from the community to adapt and test an evidence- based smoking cessation intervention. Achieving this goal is a crucial step in a larger process of establishing an essential line of research treating TUDs with people with IDDs. Through this K99 we aim to complete 40 semi- structed interviews with staff and patients actively engaged and not engaged in tobacco treatment to 1) identify barriers that contribute to low TUD treatment enrollment and high drop-out rates for people with IDDs, and 2) select and adapt an existing intervention for use with those with IDDs. Through the R00 we will utilize the results of our K99 to evaluate the feasibility, acceptability, and initial efficacy of a tailored, behavioral smoking cessation intervention in this population. The modified intervention, based on findings from the K99, will be implemented in a feasibility trial in people with IDDs. Outcomes will include intervention feasibility and acceptability (primary outcome), self-reported cigarette smoking (secondary outcome) and cigarette smoking measured by expired breath carbon monoxide (secondary outcome). The results of this project will inform the development and implementation of a larger randomized controlled trial to be conducted as part of a future R01 grant. This project will fill a profound research gap by understanding significant smoking treatment barriers and developing and piloting a tailored smoking cessation intervention for people with IDDs. This award will include substantial training and mentorship from a diverse group of K99 mentors who will supplement Dr. Regnier’s experience in the application of evidence-based treatments to IDD populations, and provide him with skills in implementation scienc...