This funding opportunity announcement (FOA) encourages applications for institutional research career development (K12) programs that propose to support intensive supervised research training and career development experiences for clinician scientists (Scholars) leading to research independence in the area of substance use and substance use disorder research. The purpose of the National Institute on Drug Abuse (NIDA) Mentored Clinical Scientist Development Award in Substance Use Disorder (SUD) Research (K12) is to encourage institutions to develop and/or sustain programs that support intensive, mentored research and career development experiences for clinician scientists. For this notice of funding opportunity (NOFO), a clinician scientist is defined as an investigator who 1) has a medical doctorate, public health doctorate, or other doctorate related to human healthcare; or 2) has a research doctorate and either clinical responsibilities or direct interaction with human subjects. Using this definition, clinician scientists (scholars) may include physicians, clinical psychologists, epidemiologists, social workers, pharmacists, behavioral scientists, etc. It is expected that these programs will provide clinician scientists (Scholars) the mentoring, training, and research experiences necessary to conduct independent research related to substance use and SUDs. Each award is intended to support Scholars for 3-4 years of consecutive 12-month appointments.