Central and eastern European countries have been and still are adapting their legal framework to the requirements of a Western market economy and the body of EU legislation, the acquis communautaire. As the harmonisation of the national legal framework to EU standards is one of the yardsticks for EU accession, most candidate countries have drafted and adopted new legislation under enormous time pressure. Sub-optimal solutions, unforeseen implementation costs and unintended side effects were unavoidable. In many cases new legislation has proved impossible to implement. This experience has led candidate countries and other transition countries to develop an interest in impact assessment. EU Member States introduced impact assessment for legal programmes about two decades ago, based on the experience that new legislation may have a considerable and sometimes unexpected, impact not only on the budget, but also on various parts of the economy and society as a whole. Today, there is an acceptance among EU Member States that some kind of impact assessment exercise should be conducted before legislative changes are introduced. Although the comprehensiveness of a particular impact assessment exercise depends on a variety of factors, e.g. the importance of the policy issue or the commitment of the respective government, the basic aim is to enhance the quality of government decision-making. Establishing or improving the administrative capacity to carry out impact assessments is crucial for both in order to provide the government with the necessary information to take informed decisions on policy options and to improve the quality of new legislation. Even applying only the basic principles of impact assessment can often avoid the necessity for immediate amendments or redrafting. This publication deals with impact assessment in a wide sense, including policy analysis (impact assessment for choosing the instrument), assessment of a policy instrument during the drafting stage and evaluation of existing laws or programmes. Special emphasis is given to impact assessment during drafting.