This paper covers the practical and technical aspects of applying transient fluid flow and heat transfer models to a real-time pipeline leak detection system. The system discussed monitors 24 batched products pipelines from a central control facility consisting of dual Data General Eclipse S/250 computers. The 24 pipelines in the system total over 3100 mi in length, ranging in size from a 13-mi, 1-station, 1-terminal, 6-in. line to a 360-mi. 6-station, 7-terminal, 30-in line. The minimum detectable leak size proven in testing is approximately 1/2 of 1 percent of maximum flow rate.