In this study, the dimensional optimization of motion and force transmitting components of a gearbox is performed by genetic algorithm (GA). It is aimed to obtain the optimal dimensions for gearbox shaft, gear and the optimal rolling bearing. GA is a non-conventional useful search technique. In genetic algorithm, the best results can be obtained within the solution space which is formed by the design constraints. With the optimization of the gearbox components, the design with smallest volume which can carry the system load is obtained. The results obtained by GA optimization are compared to those obtained by analytical methods. These obtained results indicate that GA can be used reliably in machine element design problems. (C) 2010 Elsevier Ltd. All rights reserved.