The Adult-to-Adult Living Donor Liver Transplantation Cohort Study (A2ALL) was a network of nine leading liver transplantation centers in the United States and Canada, assembled by the National Institutes of Health in 2002. Arbor Research served as the DCC under a cooperative agreement with the University of Michigan. The A2ALL study was designed to answer questions about safety and outcomes for donors and recipients of living liver donation. 

Living donor liver transplantation has the potential to streamline the future of liver transplantation by avoiding lengthy waiting periods for a deceased donor transplant, reducing ischemic time with scheduled procedures, and allowing for longer evaluation of the donor and recipient, possibly leading to decreased mortality and better long-term outcomes. However, prior to the A2ALL project, there were few answers for living liver donors about their future medical outcomes and quality of life. The A2ALL study represents the largest and longest study of living liver donors in the United States to date. Comprehensive reports from the A2ALL helped inform the transplant community and served as a benchmark for future interventions and strategies that measure and reduce risks to donors and recipients alike.​