Sustainability of organizations is directly linked to the continual improvement of business performance. Many organizations have found a way to improve performance through the establishment of management systems. To maximise benefits of the system, it is necessary also to develop and implement a well-structured performance evaluation process to assist both the business and its interested parties achieve agreed objectives, in a sustainable way. This paper considers a new methodology for performance evaluation of management systems based on the concepts of the AS/NZS ISO 14031:2000, CSA PLUS 1144 and GEMI - measuring environmental performance. The methodology is being developed at a time when there is increasing interest in social issues, as one of the three constituent parts of sustainability (social, economic and environment). The material presented is derived in part from PhD studies of Jose Flavio Coelho.