METHODOLOGY CORE ABSTRACT The Methodology Core of the CCCR will bring together investigators from diverse scientific backgrounds whose research interests are in the specific diseases of focus for this CCCR, osteoarthritis and gout, along with interests in spondyloarthritis, scleroderma, osteoporosis and musculoskeletal pain. By having rheumatology, rehabilitation and epidemiology and biostatistics investigators meet once a week together, the Methodology Core creates interdisciplinary conversations and makes available to clinician researchers methodologic expertise that would otherwise not be part of their grants or scientific projects. As in the prior MCRC, there is a focus in the Methodology Core on epidemiologic studies of established and new cohorts in osteoarthritis and gout. In addition, in the past five years we have developed expertise in addressing epidemiologic questions using large electronic health record databases, especially the Health Improvement Network (THIN). The Boston University CCCR group is well known for training young investigators, many of whom now make up a large segment of the clinical researchers in rheumatology domestically and around the world. The Methodology Core will continue to emphasize training doctoral and postdoctoral students and rheumatology fellows. The overall goals of this methodology core are to provide state of the art methodologic input into clinical research questions in OA, gout and other diseases we study and also to introduce new impactful clinical research methods into the study of these diseases. In addition to providing support for study protocols, design and statistical analysis, modern epidemiologic methods involving causal inference and Mendelian randomization will be used. Further, because they represent major components of the future of clinical research in CCCR diseases, we will include new expertise in machine learning and mobile health technologies.