Sustainability of the environment is becoming more important to public attitudes because present malpractice will create problems for the next generation. The environmental performance of companies is currently a major concern to society worldwide. Studies in environmental reporting and disclosure, conducted in the developed countries, found that no standard format and practice was concluded. Unlike most of the previous studies, this study was conducted in Thailand, a representative of countries with an emerging capital market, with two addressed issues: 1) what types of information and report should be; and 2) Whether there is an association between voluntary environmental disclosures and firms' environmental performance, economic performance, and stakeholder influence. For the first issue, the types of information and report were designed and the opinions of executives from companies listed in the Stock Exchange of Thailand and users of environmental information were surveyed. The results of the study found that environmental information including environmental policies, plans, projects, assets/expenses, benefits, law conformity, and contingent liabilities should be disclosed with reference to their magnitude. Assets/expenses was the most important element of disclosure, whereas environmental plan disclosure was the element that received the least support. The provider group confirmed that assets/expenses were important information while the user group concerned with law conformity disclosure. All respondents also supported the proposed environmental report which was separated from the financial statements. The second issue was to test the association between disclosure and its determinants: environmental performance, economic performance, and stakeholder's influence based on stakeholder theory. This study found weak association. Shareholder's influence, one party of the stakeholders, has negative association with disclosure and is statistically significant. In conclusion, this report could be a guideline for developing a standard for environmental reporting. The implementation should be step by step. At the beginning stage, environmental information especially assets/expenses and law conformity should be disclosed with reference to their magnitude. Later, the disclosure should develop into the full report. Further studies to resolve the problems of measurement, standard content, and standard format have to be pursued.