Forest certification was introduced in the early 1990s to address concerns of deforestation and forest degradation and to promote the maintenance of biological diversity, especially in the tropics. Initially pushed by environmental groups, it quickly evolved as a potential instrument to promote sustainable forest management (SFM). To date about 124 million ha or 3.2% of the world's forests have been certified by the different certification schemes created over the last decade. Forest certification shares the aim of promoting SFM with another tool, namely criteria and indicators (C&I) for SFM. C&I sets are mainly developed for the national level to describe and monitor status and trends in forests and forest management. They also provide an essential reference basis for forest certification standards, which set performance targets to be applied on a defined area. Progress in developing these two different tools has been significant. After 10 years of implementation, it is evident that the original intention to save tropical biodiversity through certification has largely failed to date. Most of certified areas are in the temperate and boreal zone, with Europe as the most important region. Only around ten per cent is located in tropical countries. The standards used for issuing certificates upon compliance are diverse, both between certification schemes and within one and the same scheme when applied in different regions. However, they are at least equal to legal requirements and often include elements that set actually higher standards. While the quality of actual audits of the standards is of varying quality, there are indications that independent audits are an incentive for improving forest management. As a voluntary market-based tool, forest certification is depending on the ability to cover the costs incurred and thus on often-elusive green consumer sentiment. Regardless of many difficulties, forest certification has been very successful in raising awareness and disseminating knowledge on a holistic SFM concept, embracing economic, environmental and social issues, worldwide. It also provides a tool for a range of other applications than assessment of sustainability, such as e.g. verifying carbon sinks.