Multiagent systems (MASs) consist of several autonomous entities, called agents, that interact with each other to either fulfill their own interests (competition) or reach a common goal (cooperation). In MASs, negotiation is the key form of interaction that enables groups of agents to arrive at a mutual agreement regarding some belief, goal, or plan. The aim of this study is to develop a MAS that simulates the negotiation process between parties (mainly contractor and client) about risk allocation and sharing of cost overruns in construction projects. The MAS was developed using three different negotiation protocols: time-dependent concession, Zeuthen's strategy, and Zeuthen's strategy with Bayesian learning. Sensitivity analysis was carried out to test the effect of reservation value, first-offer value, and negotiation protocol on the settlement amounts. The model was also tested on three hypothetical cases. Results show that it is mainly the reservation value that determines the settlement amount of the negotiation. The developed system can be used by decision makers to understand how the risks and associated costs are shared between parties under different scenarios. DOI: 10.1061/(ASCE)CP.1943-5487.0000218. (C) 2013 American Society of Civil Engineers.