There have been concerns over Crown Prince Sultan's health
Sultan bin Abdul-Aziz, second deputy prime minister and minister of defence and aviation, has been named the new crown prince of Saudi Arabia at the age of 81.
Now the heir to the Saudi crown, there are fears over the crown prince's own health. In 2004 he had an operation to remove a cancerous growth from his stomach.
Crown Prince Sultan is a full brother of the late King Fahd, one of seven male offspring of former King Abdel Aziz's favourite wife.
The new monarch, King Abdullah, is one of King Fahd's half-brothers.
Crown Prince Sultan has been a long-term advocate of close ties with the United States, despite tensions that arose in the aftermath of the 11 September 2001 terror attacks, mainly carried out by Saudi nationals.
His son Bandar served as the Saudi ambassador in Washington for two decades before stepping down in July 2005.
The crown prince is chairman of the Higher Council for Islamic Affairs, an organisation that provides funds for Muslim communities around the world.
Because of this role, his name has been raised in connection with claims that Saudi money has been paid to Islamic charities with alleged links to terrorist groups - allegations strongly denied by the prince.
Development and conservation
Crown Prince Sultan was born in Riyadh in 1924.
He is one of the so-called Sudayri seven, the seven sons of Hassa bint Ahmad al-Sudayri, the former King Abdel Aziz's favourite wife.
He received a traditional education in his father's court and made his first major appearance on the public stage in 1947 when he was appointed governor of Riyadh.
Sultan has been a key political figure in Saudi Arabia for decades
In 1953 he became minister of agriculture, and two years later he was handed the communications portfolio.
Crown Prince Sultan has held his current post in the Ministry of Defence and Aviation since 1963.
In this capacity he has been closely involved in the development and expansion of the Saudi national airline, Saudia, and the construction of the rail link between Dammam on the Gulf coast and Riyadh.
He has also overseen the development and modernisation of the country's armed forces, turning Saudi Arabia into one of the world's largest arms procurers.
He commands the armed forces, although few are posted in Riyadh itself to allay fears of a possible coup.
In his private life Crown Prince Sultan has an interest in nature and conservation. He was the founder, in 1986, of the Saudi National Commission for Wildlife Conservation.
In 1982, when King Fahd's reign began, Crown Prince Sultan was appointed second deputy prime minister.
He has recently dampened hopes that a male-only local election held in 2005 could herald wider reform, voicing his fears that "illiterates" could win power in a more open vote.