Summary: Autonomous agents are being used in an increasing number of applications. The agents operate in complex environments and, over time, conflicts inevitably occur among them. Negotiation is the predominant process for resolving conflicts. This paper presents a generic negotiation model for autonomous agents that handles multi-party, multi-issue and single or repeated rounds. The model is based on computationally tractable assumptions and accounts for a tight integration of the individual capability of planning and the social capability of negotiation. This paper also describes an experiment conducted to evaluate the model in different types of situations. The experimental results confirmed a number of well-documented conclusions about human negotiation.