We examine the determinants of adherence to U.S. Securities and Exchange Commission (SEC) mandated disclosures of environmental sanctions. Our sample includes non-superfund U.S. Environmental Protection Agency (EPA) sanctions between 1996 and 2005. Our results suggest that firms are more likely to provide sanction disclosures if they operate in environmentally sensitive industries, are subject to larger penalties and are voluntarily participating in a supplemental environmental project. Our results also suggest that firms are less likely to disclose sanctions involving judicial proceedings. Overall, we find that voluntary disclosure incentives impact compliance with mandatory reporting requirements. Although incentives exist for firms to comply with mandatory disclosures, our results suggest that increases in mandatory environmental accounting disclosures may not be effective under the current regulatory system despite the use of bright-line materiality thresholds. Our study contributes to the current and ongoing debate about the role and effectiveness of environmental risk disclosure mandates in providing information to the marketplace, as well as "mandated disclosure" rules in general. The value attributed to current and potential environmental disclosure regulations cannot be thoroughly understood without examining disclosure compliance with existing regulations. From an environmental and sustainability disclosure perspective, our findings are particularly germane since these disclosures focus on risks, liabilities, or other reputational shortcomings of the firm.