We describe a GOMS model of a ship-board Radar Operator's behavior while monitoring air and sea traffic. GOM S is a technique that has been successfully used in Human-Computer Interaction to generate engineering models of human performance. Based on the GOM S model developed, we identified those portions of the task where an intelligent agent would be most able to assist operators in the performance of their duties, and the nature of the knowledge that will be required for the task. W e present the results of a simulated execution of the model in a sample scenario, which predicted the operator's responses with a high degree of accuracy.