Interacting Multiple Model (IMM) estimator is used extensively to estimate trajectories of maneuvering targets in cluttered environment. In the standard tracking methods, it is assumed that movement of target is applicable to a certain model and the target could be monitored via the usage of status predictions of that model. However, targets can make different maneuvering movements. At that time, expression of target dynamic model with only one model can be insufficient. In IMM approach, target dynamic model is expressed with more than one model capsulating all maneuvering movements or with one model with different noise level values. This thesis investigates the tracking of the maneuvering ground targets in cluttered environment via IMM estimator with constant velocity model with low/high process noise, coordinated turn model and move-stop-move model. The selection strategies of models are highlighted and the state errors are calculated to evaluate the performance of IMM estimator.