LivSim is an extensible, open-source discrete-event simulation of the allocation of livers in the US Organ Procurement and Transplantation Network (OPTN). The most recent version, LivSim 1.11, is written for Python 3.4.2 and is designed to work in tandem with the Liver Simulated Allocation Model (LSAM) (v. Aug 2014) as a separate module. For more information, refer to the LivSim_Manual.pdf.