Reticle systems are considered to be the classical approach for estimating the position of a target in a considered field of view and are widely used in IR seekers and trackers. This type of seeker is most suitable for tracking airborne targets such as aircraft and missiles. With an image processing system, where the reticle pattern as well as the received radiation are described as digitized images of rather high resolution, simulations can easily be performed. The method can be used for the simulation of systems with spinning reticles as well as of systems utilizing fixed reticles with an off-axis rotating lens or mirror. In this manner any arbitrary reticle pattern can be studied and the pattern can be easily altered. Simulations were performed using a TERAGON® 4200 image processing system. The simulation method and the possible signal processing methods for different types of reticle systems are described. These systems are mainly used as seekers in surface-to-air or air-to-air missiles. The simulation model presented has been used in threat analysis and in studies on the effects of various types of countermeasures, e.g., flares and jammers. The result of the simulated reticle output signals has been validated by the use of different reticle seeker hardware.