Expectations that corporations be accountable for their "triple bottom line" performance have never been greater, yet many sustainability reports provide little in the way of third party assurance. Although such assurance is on the rise internationally, KPMG's 2005 International Survey of Corporate Responsibility Reporting finds that U.S. companies are dramatically lagging behind, providing fewer assurance statements than firms in 15 other industrialized nations. It appears that despite the Sarbanes-Oxley requirements for transparency in corporate affairs and governance, most U.S., firms are still reluctant to submit to, or pay for, independent assurance. And those firms that do hire external assurance providers face criticism that the assurance statements only verify reporting processes rather than the data itself. Are these criticisms fair? How far should assurance providers go to guarantee the credibility of non-financial data? And how can such assurance efforts better reflect the concerns of stakeholders?