Technological innovation can help realise environmental objectives in a less costly manner than would otherwise be the case. Thus, understanding the role that technological innovation can play in achieving environmental objectives is important for policy debates. However, the relationship between environmental policy and technological innovation remains an area in which empirical evidence is scant. In an attempt to bridge this gap, the OECD has examined the relevant issues, using patent activity as a measure of technological innovation. Three case studies have been undertaken: abatement technologies for wastewater effluent from pulp production, abatement of motor vehicle emissions, and development of renewable energy technologies. On the basis of patent data, the nature, extent, and causes of innovation in each of these areas have been explored. While a particular focus has been placed on the role of environmental policy in bringing about the innovation documented, it is recognised that other factors play a key role in inducing innovation that has positive environmental implications.