An environmental accident at a Placer Dome mine triggered a contagion effect across the Canadian mining industry. The decline in equity prices was moderated by prior disclosure of a high-level commitment to environmental management. Investors appear to interpret this information as a signal of expertise in the management of environmental risks and costs. The same companies are positioned to make the most credible financial disclosures about environmental management, and yet the evidence suggests that financial disclosures themselves have a negative impact on company value. There may be a miscommunication between investors and analysts on the one hand and mining company executives on the other, which could explain why mining company managers report their companies’ shares are undervalued.