To find a way to measure sustainable performance its three components economic, environmental and social performance have to be defined clearly and both assessed and improved properly. As it is almost impossible to do this simultaneously for these three components, strategies for improving sustainable performance have to be developed. The EPM-KOMPAS approach, which aims at supporting small and medium sized enterprises (SMEs) in the manufacturing industry in their efforts towards sustainability, provides an instrument to measure, assess and systematically improve the environmental and economic performance of SMEs. This approach offers SMEs an opportunity i) to collect relevant environmental data, ii) to choose the most relevant master parameters, which are the first needing improvement, iii) to set objectives for the improvement and iv) to assess the effectiveness of measures implemented. After a short introduction this paper places emphasis on the special environmental assessment method in EPM-KOMPAS, which has been developed especially to support SMEs having large difficulties to choose the most relevant environmental aspects, on which their management of environmental performance should focus. This assessment method considers the data available in SMEs in the manufacturing industry and supports them by offering different alternative possibilities for assessments first to rank environmental aspects and, then, to decide which one(s) should be controlled. With this decision SMEs are enabled to set objectives, to determine measures and to assess the success of these measures.