This Notice of Funding Opportunity (NOFO) supports applications to develop and implement investigator-initiated single site clinical trials including efficacy, comparative effectiveness, pragmatic and/or implementation research clinical trials. These trials may include ones that test different therapeutic, behavioral, and/or prevention strategies. The application should address project management, subject recruitment and retention, performance milestones, scientific conduct of the trial, and dissemination of results. Key aspects of this opportunity include: • Clinical trials must be relevant to the research mission of the NHLBI and meet the NIH definition of a clinical trial. • The multiple PD/PI model is strongly encouraged but not required. • Applicants are encouraged to include a PD/PI with expertise in biostatistics, clinical trial design, and coordination. • The application should present the scientific rationale for the clinical trial and a comprehensive scientific and operational plan that describes it.