CTBTO staff and Advanced Science Course participants describe the simulation of point of entry negotiations for a CTBT on-site inspection, to verify whether or not a nuclear explosion has taken place. 70 participants attended the Advanced Science Course “Around the Globe and Around the Clock: The Science and Technology of the CTBT” in Vienna in November 2012 and hundreds more followed the course online. The two-week course culminated in the simulation, in which course participants played the Inspection Team and the Inspected State Party to negotiate how a fictional inspection might take place. The simulation tested all the participants had learned during the course and gave them a chance to demonstrate their CTBT knowledge and negotiation skills.