Is the adoption of best practice in business associated with improved environmental performance? And whatmethods can be used to assess and compare the environmental practices and performance of different companies? In thispaper, through case analysis, the business environmental practices and performance of five companies in the manufacturingsector were examined and scored. Assessing these companies practices and performance according to "The best practicemodel" designed by Australian Manufacturing Council (AMC, 1994). The finding shows that there is strong correlationbetween environmental practices and performance of companies (r=0.85, p<0.05), and indicates that corporate payingattention to environmental issue will improve its all performances in business.