This paper for the first time presents the new interface between CAOSS and MSC/NASTRAN. CAOSS® (Computer Aided Optimization System Sauter) is an optional finite element module for the efficient sizing, shape and topology optimization. The introduction gives a survey on the program itself and on its history. To begin with, the first chapter gives an overview of the optimization type (sizing, shape and topology) and the state-of-technology. In addition the principal differences between the mathematical programming methods and the methods based on optimum criteria are explained. A comprehensive chapter reveals the theoretical backgrounds of the optimum criteria for shape and topology optimization purposes as well as the especially developed controllers created by the authors. The interaction of CAOSS and MSC/NASTRAN and the optimization options new to the MSC/NASTRAN user in conjunction with CAOSS are emphasized. Finally industrial application examples give an impression of the capabilities.