Their total net worth accounted for 64% of the aggregate wealth of the region's 65 billionaires. Interestingly, only one in the top 20, Mohammed Al Amoudi, actually makes his fortune from oil; the rest are merely beneficiaries from all the oil money sloshing through the region.

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That is especially true in Saudi Arabia, home to 25% of the world's oil reserves and seven members of our top 20. Their wealthiest citizen, and also the region's richest, is prominent: Saudi investor Prince Alwaleed Bin Talal AlsaudPrince Alwaleed Bin Talal Alsaud ranked 13th in the world in March, then worth $20.3 billion. In July, the prince took public his Kingdom Holding Co.Kingdom Holding Co., a conglomerate of banking, media, real estate and hotel investments, raising $2.3 billion. He still has a substantial stake in U.S. financial giant Citigroup.

Another Saudi investor, Maan Al-Sanea, made news in April when he disclosed a 3.1% stake in HSBCHSBC. The announcement propelled the former air force pilot--and, until then, low-profile businessman--into the limelight, and helped boost his fortune, which we estimated at $7.5 billion in March, to at least $10 billion.

Like Prince AlwaleedPrince Alwaleed and Al-Sanea, a number of these moneyed Middle Easterners are investing overseas. Israeli property tycoon Yitzhak Tshuva bought Manhattan's storied Plaza Hotel in 2005 for $675 million. Further downtown, his fellow countryman, diamond mogul Lev Leviev, paid a reported $525 million for the historic New York Times building in April. The pair are joined in the top 20 by four other Israelis, including the only woman in the group, Shari Arison.

Across the Red Sea, business has been especially good for Egypt's risk-taking Sawiris family and its Orascom empire. Oldest son NaguibNaguib saw his fortune nearly quadruple in 2007 to $10 billion thanks to his Orascom TelecomOrascom Telecom's aggressive expansion into Greece and Italy. In addition, the company has mobile customers in seven fast-growing emerging markets in Asia, Africa and the Middle East. Father Onsi and brother Nassef are also chasing developing markets: Their Orascom ConstructionOrascom Construction company recently opened cement plants in South Africa, Algeria and Iraq.

Banking is actually the most common source of wealth among the region's 20 richest, with half a dozen making their money in that industry. Among these financial types are Dubai's wealthiest banker, MashreqbankMashreqbank's Abdul Aziz Al GhurairAbdul Aziz Al Ghurair, worth $8 billion in March, and Husnu Ozyegin, Turkey's only billionaire in the top 20 (another 24 are billionaires). Ozyegin made the bulk of his $3.5 billion fortune in banking, as founder of Finansbank, then sold his shares to National Bank of Greece in 2005.

These days he stays busy (and wealthy) as owner of a hotel, shopping mall and eight Marks & Spencer retail stores in Turkey and Russia. Saudi Arabia's Al Rajhi family, whose eponymous bank manages the wealth of everyday Saudis, is perhaps the region's oldest banking family. Worth a collective $15.9 billion, the four aging Al Rajhi brothers (two of whom rank in the top 20) have controlled the bank since it began in the 1940s as a desert trading post.

Looking ahead, expect new fortunes and big investments to come out of the region in time for our 2008 billionaire rankings.

By Devon Pendleton

© Forbes 2007