In this paper, a methodology for balancing assembly lines with smoothed work station assignments is presented Smoothed work station assignment constitutes an additional criterion during the design and development of assembly lines characterized by a large number of tasks, a small variation of task-times and a small number of precedence constraints with regard to the total number of tasks to be performed . Assembly lines having the above features are common in industrial environments. In those cases the application of the suggested methodology leads to a more efficient organization of the assembly line. This is confirmed by the successful application of the suggested methodology in redesigning the assembly line of a jeep-type vehicle in a major Greek company.