Turkish Prime Minister Recep Tayyip Erdogan, Azerbaijani President Ilham Aliyev, Georgian President Mikheil Saakashvili, and Kazakh Prime Minister Daniyal Akhmetov were all present for the ceremony.
So too was U.S. Deputy Energy Secretary Clay Sell, who called the $3.9 billion pipeline "an effort of great strategic and economic importance to the countries involved."
Saakashvili said the project enhanced the independence of all countries involved.
"This project brings to all of us security, stability and a promise of a better future," Saakashvili said. "It's not only about energy independence or economic independence. This project is about independence -- about real independence for our countries."
British Petroleum chief executive John Browne was also in Ceyhan and said the opening of the BTC pipeline "changes the energy map of the world."
When it reaches full capacity around 2010, the pipeline is expected to carry 1 million barrels of oil daily.
Oil rich Kazakhstan says it will also join the project.
MORE: For coverage of this topic from RFE/RL's Russian Service in Russian, click here.
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HOW MUCH OIL? The U.S. Energy Information Administration has estimated that the Caspian could hold between 17 billion and 33 billion barrels of proven oil. ("Proven reserves" are defined by energy experts to be 90 percent probable.) Other experts estimate the Caspian could hold "possible reserves" of up to 233 billion barrels of oil. ("Possible reserves" are considered to be 50 percent probable.) By comparison, Saudi Arabia has 261 billion barrels of oil and the United States 23 billion...(more)