Our experience in development decision support systems (DSS) for machining linedesign and balancing is presented. It concernsmachining lines for the automotive industry. Inorder to offer to machining line designers a cognitive aid for early design stages such DSS aredeveloped. The objective is to assist the decision makers in finding the configuration of a new linethat will meet quality and productivity requirements and minimize the investment costs. Thecurrent versions of DSS are oriented to design of mass production machining lines with multi-spindle heads as well as reconfigurable lines composed of machining centers. This decision supportsystems are based on mathematical models and methods which were devised to provide thedesigners with the optimal parameters of new line configuration including the required number ofworking stations of different types, the number ofmachines at each station and spindle heads ateach machine. The system is implemented under Autodesk Inventor and includes the modules forpart modeling, process planning and machining system configuration. Its modular character andopen architecture make upgrading with new mathematical tools suitable for other manufacturinglines easy and fast. Moreover, it can be employed either as a separate software or integrated in aProduct Lifecycle Management (PLM) tool.