Project Description/Abstract A urea cycle disorder (UCD) is an inborn error of metabolism caused by a deficiency of one of the enzymes or transporters in the urea cycle, which is responsible for removing ammonia from the blood and brain. Ammonia is toxic to the central nervous system and its accumulation can lead to coma and death in the short term, and brain damage to those who survive hyperammonemic (HA) events. In recent years, morbidity has decreased; however, neurocognitive effects and potential liver damage have emerged as major clinical features. There is currently no cure, although novel therapies have improved the outcome for many affected individuals. This R13 conference grant application requests funding for the 5th International Symposium on Urea Cycle Disorders, to take place from September 22-24, 2021 virtually as a satellite symposium to the 14th International Congress on Inborn Errors of Metabolism (ICIEM), which will be held as a hybrid conference, virtually and in-person, in Sydney, Australia, from November 21-23, 2021. The scientific symposium, titled, ?Mapping Progress: Current Concepts and New Insights in Urea Cycle Disorders?, will be organized by the Urea Cycle Disorders Consortium (UCDC), the European Registry and Network for Intoxication Type Metabolic Diseases (E-IMD), and the National Urea Cycle Disorders Foundation (NUCDF) patient advocacy group. UCD Satellite Symposia to the ICIEM Conference were held previously in in Vienna in 1997, Sydney in 2003, La Jolla in 2009, and Barcelona in 2013. Proceedings from these symposia were published in the Journal for Inherited Metabolic Disease and Molecular Genetics and Metabolism. Interest and participation have increased with each meeting with 265 attendees in 2013. We expect 400-500 participants to attend the 2021 virtual symposium. NIH support will help the UCDC continue this tradition, bringing together UCD experts from around the world to share research discoveries and encourage and accelerate collaborative research. Trainees will be encouraged to attend the conference to supplement their training, participate in mentoring sessions, and submit abstracts to share their research with leaders in the UCD field. The virtual platform will help expand engagement with partners from around the globe, including under-resourced countries, to share in exchange of best clinical practices and research. The proposed symposium will be divided into three sessions on consecutive days for approximately three hours each day. The sessions will focus on 1) clinical management and patient outcomes around the globe 2) biomarkers and pathophysiological insights suggesting novel therapeutic approaches and, 3) early detection and new treatment principles. Time is allocated for discussion using interactive virtual network sessions and a poster session. Proceedings will be published by Molecular Genetics and Metabolism.