Optimization of mechatronic systems using the software package NEWOPT/AIMS Optimization of mechatronic systems is an interactive process which requires the iterative application of several different computer algorithms and decisions of the designer depending on the demands of the optimization problem. In this paper the software package NEWOPT/AIMS for optimization of multibody systems is presented. For the application to mechatronical systems the software is augmented by additional methods for sensitivity analysis and scalar optimization. par The software package includes algorithms for simulation, sensitivity analysis and optimization. Sensitivities can be provided by the efficient semi-analytical adjoint variable method, automatic differentiation or finite differences. For multicriteria optimization the designer may choose from different strategies and algorithms. par The interactive optimization process is supported by an interface designed for a simplified and intuitive usage of the software tool. par The optimization procedure is demonstrated for two complex systems, a manipulator with parallel kinematics, and a model of a reconstruction of a damaged human middle ear.