How can we distinguish between high-quality statistics and data whose quality is poor? And what exactly do we mean by the “quality” of statistical data? Do quality standards exist for statistics? If so, who established them? At present, when users have practically unlimited access to statistical information but often feel bombarded by the media with sometimes conflicting data, the ability to identify high-quality statistics is of paramount importance. This chapter illustrates the basic concepts developed to ascertain the quality of statistical data, and the initiatives launched at the international level to assess the quality of statistics produced by national statistical offices and other producers of official statistics. Given that the international comparability of statistics plays a key role in the decision-making process of major international organisations, the IMF, the OECD and European authorities have worked particularly hard to develop models for assessing statistical quality.