The report describes the national loop of the Advanced Utility Simulation Model (AUSM), simulating strategic planning in the electric utility industry. Acting as a preprocessor to the second component of AUSM (the state model), the national loop simulates decisions about generating and scrubber capacity additions, fuel choices, and interstate electricity transfers. These decisions influence (and are influenced by) coal prices, providing a partial equilibrium model of the coal-electric utility market. Three modules comprise the national loop: the Multi-Period, Multi-State Module (MPMS), the National Coal Supply Module (NCSM), and the Coal Market Equilibrium Module (CMEM). Electric utility decisions are made in the MPMS and coal demands calculated. These are passed to the NCSM where coal prices are calculated. After being checked for convergence (which signals achievement of equilibrium), prices are passed to the MPMS for re-simulation of coal demand. This process continues until equilibrium is achieved or until it is determined that no equilibrium exists. In general, the report contains all of the principal equations and operating concepts for the national loop.