Co-determination between workers and management in a firm could be efficient if they were cooperative each other in dicision making. Efficiency and co-determination is compatible in this case. But if workers pursued the quality of working life in a production system by introducing for example a democratic form of work organization or long work cycles in an extreme level, the efficiency might be low at least in a short time. The relation between efficiency and the quality of workung life is among the trade-off area in this case. However, in the long run, workers can have the opportunity to improve the efficiency by systematic special job training. Two examples of auto plants are compared in the article to explain the above hypothesis. The first one is the Uddevalla factory of Volvo in Sweden and the second is Saturn Corporation, the GM's subsidiary.