The first mention of clinical trials in a legal document occurred in Turkey many years before the Helsinki Declaration or Belmont report; issued in 1926, the Code of Pharmaceutical Products and Preparations No. 1262 law carries the statement: "Experimental drugs can be used in a patient only by his/her permission". Then the other regulation is the Regulation on Medical Deontology, dated 1960, and still in force. Article 10 and 11 of this Regulation address physicians and dentists who are conducting research. After periods of misconducted and ill-designed studies, the modem era of clinical trials began in 1993 with the introduction of the "Drug Research Bylaw". This document was directly influenced by the initial drafts of ICH-GCP Guidelines, and some parts were very similar. This became the main document that regulates the conduct of clinical trials in Turkey. A good clinical practice (GCP) guidelines document was added in 1995. On the other hand, an amendment made to Article 90 of the New Turkish Penal Code No. 5237 of 26 September 2004, which will come into force on 1st April 2005, envisages that in conflicts between international treaties concerning basic rights and freedoms and national laws, priority will be given to the international treaties. Therefore, in Turkish law, international treaties concerning basic rights and freedoms are given precedence as compared with national laws and other regulations. The Article stipulates the conduct of research on conditions such as not violating human well-being and dignity.