This study summarizes results from six case studies in Sustainable Product Development, based on a method developed in the Nordic Project for Environmentally Sound Product Development. In all, but one case, there are reported significant improvements in environmental performance of new products, compared to existing reference products. Proposed options for improvement would increase purchase cost in as many cases as it was reduced, whereas life cycle cost for the user of the product was mainly influenced positively. The improvement options did not influence on important customer quality parameters in most cases, and there was as many positive as negative relationships. Based on the results from the study, it is not possible to give a general rank of priorities of strategies and options for improvements. What are the best solutions depend to a high degree on the external conditions of the product systems, and what types of products are examined. A scenario model, based on real product data, shows that the optimal life time of a product with the most significant environmental impacts related to the user stage might approach the innovation cycle time, if increased eco-efficiency is the driving force of the innovation process. To reach a level of global sustainability, it is not sufficient to improve the eco-efficiency of each product as such. Major changes in the infrastructure for energy production, distribution and consumption, in transport infrastructure systems, and in management of material cycles in the society is necessary. It is proposed to use eco-effectiveness as a measure for environmental improvement of product systems, as an alternative to ecoefficiency.