Many factors influence the performance and life of the apex seal system in a rotary engine. These considerations include basic configuration, material and dimensions of sealing elements, lubrication conditions, seal and surface temperatures, and seal loading. These parameters and particularly their interactions are not well understood.The objective of this investigation was to create mathematical models capable of explaining the dynamic behavior of the apex seal system. These models enable us to: 1. Understand present apex sealing system loads and how they are influenced by design and material parameters. 2. Allow product engineers to assess the influence of proposed design changes on apex seal performance. Two models were created. The first models the effect of apex seal to rotor slot friction and deformable rotor housings. The second model considers the effects of inertia forces, indicator diagram pressures, friction forces, and the geometry of the apex seal and rotor slot.