The National Cancer Institute (NCI) of the Department of Health and Human Services is issuing a funding opportunity for the assay validation of high-quality biomarkers for cancer clinical studies. This initiative invites applications through a cooperative agreement mechanism (UH2/UH3) where projects focus on the analytical and clinical validation of molecular, cellular, and imaging markers crucial for cancer detection, diagnosis, and treatment response monitoring. The funding supports both phases: the UH2 phase for analytical validation, which lasts up to two years, and the UH3 phase for clinical validation spanning three years. Collaborations among investigators from diverse fields are essential to ensure successful assay integration into cancer trials. Key eligibility criteria include a proven working assay with human samples and the ability to justify its clinical relevance. Applications must propose specific milestones for transitioning between the UH2 and UH3 phases. The initiative aims to overcome regulatory challenges and support the refinement of assays needed for effective cancer treatment, prevention, and control studies, with the ultimate goal of making established assays accessible for clinical application in the healthcare community.