An experiment is used to investigate two important factors associated with environmental investment decision-making by managers: the regulatory regime in which the firm operates and the nature of environmental information used as a decision aid. Two regulatory regimes are examined, a command and control regulatory regime and a voluntary self-regulatory regime. Two accounting systems are contrasted, environmental management accounting and conventional management accounting, thereby providing a 2 נ2 experimental design for the empirical study. The paper considers environmental investment decision-making by different types of managers working in the Australian offshore petroleum industry. These empirical results indicate that environmental accounting information has a more significant influence on the willingness of managers to incorporate environmental considerations into investment decisions and to avoid future environmental risks, than does the type of regulatory regime.