The issue of Special and Differential Treatment (SDT) of developing countries in the WTO system has been a subject of debate for a number of years. As the international trading system has developed over time, and grown more complex, the importance of SDT has increased. In the ongoing WTO-negotiations under the Doha Development Agenda, SDT is seen as a key issue. Consequently, there were compelling grounds to undertake a comprehensive review of the special rules and benefits for developing countries provided for under WTO rules. The study analyses the development of the provisions for special and differential treatment within the WTO system and the actual and potential development effects of existing provisions. It puts forth a number of suggestions for how to improve the current system.