This chapter explains the evolution of the Common Market Organisation (CMO) in agriculture. It starts with the original principles of the European Union’s (EU) agricultural market and price policies and discusses successive reforms of some key CMOs. Market measures have clearly become less important, but they remain an essential part of the policy mix of the Common Agricultural Policy (CAP). The reduction of the scope of classical market measures has been accompanied by a stronger emphasis in the CAP on a regulatory environment to strengthen farmers’ organisational structures. To improve farmers’ and small- and medium-sized businesses’ position in the food supply chain, a new directive has been prepared on unfair trading practices.