The INTEGRATE-LMedC consortium will develop a new concept to guide and support decision-making for the next-generation research infrastructure (RI) to facilitate efficient utilization and harmonization of large medical cohorts (LMedC), and to accelerate scientific and medical breakthroughs in Europe and beyond. Achievement of the ambitious objectives will only be possible through the integration of 11 highly interdisciplinary partners including established ERIC / ESFRI infrastructures such BBMRI, ECRIN, EIRENE and EBRAINS with unique expertise in conceptualizing and implementing European RIs. The partners will generate a gap analysis to identify what is missing of cohort data and samples, RI tools and services, quality measures, governance models, user needs and the barriers for efficient utilization of these cohorts and RI, including ethical and legal frameworks. To identify IT technologies and architecture for suitable data stewardship and long-term availability of European RIs, the partners will prepare for a feasibility study for federated data analysis of LMedC. The feasibility study will be based on two examples of use-cases: one stroke case using data from medical health registry data and one case using data from longitudinal population-based studies with different technical, legal, and ethical challenges. To ensure availability of data and samples related to existing and future LMedC studies and their re-use for secondary research, the partners will develop a concept outline including a governance plan and guiding principles for data access policies and data protection policy, whilst considering the FAIR principles and ELSI issues. An overarching RI concept to manage, integrate, and sustain LMedC studies will be developed, including an initial financial and operational plan for the implementation of the new RI outlining new services and access opportunities for the research community.