Member companies of the International Council on Mining and Metals (ICMM) have committed to publish externally assured sustainability reports. This paper evaluates the quality of assurance provided to those companies by analyzing the extent to which a sample of their assurance statements met minimum recommended contents. It also seeks to understand the implications of the recently launched ICMM Assurance Procedure. Nine out of the sixteen companies hired assurance in the period analyzed. Their statements mirrored several quality problems highlighted in previous studies. The extensive scope limitations and diversity of verification criteria employed by assurors indicate that mining companies had significant control over the practice. The Assurance Procedure might bring more consistency and breadth to the verification process. The extent to which it will contribute to increased trust in reported information will depend on several factors, including how assurors may interpret the procedure's requirements. Directions for further research are discussed. Copyright © 2010 John Wiley & Sons, Ltd and ERP Environment.