In recent years, the role of the environmental risk management has become increasingly significant to multinational corporations. Corporations from the United States and elsewhere are now undertaking aggressive assessments of environmental regulatory compliance, and are incorporating environmental due diligence into transactions such as mergers, acquisitions, joint ventures, and divestitures. The first step toward assessing compliance often involves interpretation of complex, vaguely written environmental statutes and regulations. Matters are made more difficult by the fact that each governmental structure is different, and environmental controls inevitably will be administered in ways unfamiliar to foreign companies, even in countries which have emulated the United States’ system of environmental regulation. This article provides an overview of environmental requirements in Canada, primarily from the viewpoint of one already familiar with the United States regulatory framework. The article begins with an introduction to Federal laws and to the interrelationships between Federal and Provincial law and enforcement. It then focuses in greater detail on environmental laws in Ontario. That province is second only to Canada as the largest trading partner of the United States. American businesses conduct an increasingly diverse array of operations in Ontario, including manufacturing, real estate development, and capital investment, all of which come under extensive environmental regulation. Ontario is also the most industrialized province of Canada, and accounts for approximately one-half of the total volume of hazardous waste generated in Canada.