ISO registration has become one of the key elements in the implementation of total quality management. However, the opportunity for ISO-certified companies to reap the organizational benefits is influenced by the effectiveness of continuous improvement in ongoing operations. In this paper, an analytical approach based on data envelopment analysis (DEA) is proposed for measuring the relative efficiency of an ISO 9000 certified firm's ability to achieve organizational benefits. The 'best in class' of ISO performers can be further identified on the basis of their ranking with efficiency score. The results also recognize specific areas where improvement is needed in an inefficient or poor ISO performer. By careful examination of these areas, managers can detect their organization's policy constraints and evaluate the effectiveness of managerial activities.