Corporate sustainability as a newly defined concept is based on five main pillars of environment, business excellence, innovation, governance and human contributions. Among these pillars, environment is an important one since it has a wide common area with other pillars. In this paper, environmental sustainability as an important challenge to achieve a sustainability program in any corporation is discussed. This paper develops some important metrics to assess the environmental sustainability program of any given corporation. Moreover, as there are some overlaps among environment and other pillars of sustainability, these similarities and overlaps will be discussed. Finally, the application of introduced metrics in top five Fortune companies will be illustrated to accredit the practicality of the introduced metrics.