The Relationships between Reporting Format, Environmental Disclosure and Environmental Performance: an Empirical Study 1. Introduction The evolution of corporate environmental disclosure has been highly topical over the past three decades (Gray et al., 1995; Thorne et al., 2014). Historically, annual financial reports were used as essential documents to communicate with key stakeholders, with environmental reporting viewed as a supplement to financial reporting (Gray et al., 1995). More recently, to meet key stakeholders' growing demands, large companies publish standalone reports to disclose their environmental information (Clarkson et al., 2008; KPMG, 2011; Cho et al., 2015). The standalone reports become remarkable as they "represent a clear engagement of corporations with the increasingly critical issues of environmental and social responsibility" (Michelon et al., 2015, p. 63). Little effort, however, has been made to examine the impact of corporate reporting format on environmental disclosure. Reporting format, in this paper, refers to where a company discloses environmental information. Following Rupley et al.'s (2012) classification, we identify environmental information disclosed in standalone reports as 'companies' environmental reports (CERs)'; we identify environmental information disclosed in annual financial reports as 'noncompanies' environmental reports (Non-CERs)'. Also, we identify companies which disclose environmental information in standalone reports as 'CER companies'; we identify companies which combine financial and environmental information together in annual financial reports as 'Non-CER companies'.