At a time when there was great attention and intense public controversy surrounding clinical (especially multinational) research, the 52nd general assembly of the World Medical Association (WMA) adopted the 5th revision of the Declaration of Helsinki (in October, 2000)-available at www.wma.net. These revisions are the most substantial adaptations since those adopted by the 29th WMA assembly in October, 1975. The commitment to revision of the declaration acknowledged that deficiencies and disagreements in interpretation needed to be corrected and that ethical standards evolve. Nevertheless, this revision process resulted in a controversial version of the declaration. Reports on the revisions have focused mainly on clinical trials that use placebos; but because of the role of the Declaration of Helsinki in the ethics of research, a more thorough examination is needed. Here, we analyse the process of revision and the major changes made to the declaration.