The study aims at identifying which environmental information are disclosed in the administration reports by electrical companies listed in the Corporate Sustainability Index (ISE). A descriptive study, with a qualitative approach, was conducted through documental analysis, from the content analysis of the environmental information disclosed by the companies. The sample of 11 companies in the electrical industry was drawn from the population of 30 open capital companies listed in the ISE. For the analysis of the administration reports from 2006 to 2008, 8 environmental categories and 36 subcategories proposed by Rover et al. (2008) were considered. The survey results show that the 8 environmental categories had subcategories disclosed in the administration reports of the companies. The most disclosed subcategories were: a statement of current and future policies and practices; any mention of sustainability; and biodiversity conservation. The subcategories not disclosed were: the process of storing/packaging; efficient use and reuse of water; leaks/spills; use of wasted materials in the energy production; discussion of concern about a possible lack of energy; accounting practices of environmental items; environmental insurance; and environmental tangible and intangible assets. It was concluded that the research findings are consistent with the previous studies, and that most of the information disclosed intend to assign positive image to the companies, thus showing the need for standardization of environmental information disclosure.