AIIC (Association Internationale des Interprètes de Conférences- International Conference Interpreters Association) is the biggest and the most prestigious international interpreters' association with members all around the world.
AIIC imposes its ethics code and minimum standards concerning equipment and working conditions to its members in order to make it possible of them to offer their best. Membership also constitutes a guarantee for the quality and professionalism of an interpreter. Although even in AIIC you will find not all its members are equally good, they are all experienced, highly qualified and committed to serve their clients in the most professional way. To give you an example from everyday life, think of AIIC as a German car maker: most people take it for granted that a German car is trustworthy and made of high quality materials!
More information on AIIC and a complete updated list of its members can be found at www.aiic.net.
You can also read AIIC's code of ethics and its professional standards.