This publication offers a general introduction to sustainability impact assessment, which is an approach for exploring the combined economic, environmental and social impacts of a range of proposed policies, programmes, strategies and action plans. Such assessments can also assist decision-making and strategic planning throughout the entire policy cycles. It is not an in-depth or detailed user manual, but rather outlines basic principles and process steps of sustainability impact assessments, drawing on examples from Switzerland, Belgium and the European Commission, among others. This publication is a valuable source of information for policy makers on sustainability impact assessments.