Back in September 2006, Wynn Resorts CEO Steve Wynn was spending two hours each day on Chinese lessons. At age 65, Wynn is worth $3.9 billion -- yet he's still learning new tricks.

Why? Because the Wynn Macau -- Wynn's latest megacasino -- was getting set to open just off the coast of China. That's right on the doorstep of some 3 billion potential customers.

Big bets for big paydays
How has the Wynn Macau fared? Pretty well.

But Steve Wynn isn't the only billionaire going gaga over foreign markets. Wynn rival and Las Vegas Sands CEO Sheldon Adelson, himself worth $28 billion, is making a similar investment in Macau's potential. Then there's the large number of companies, from Whirlpool (NYSE:WHR) to Caterpillar (NYSE:CAT), that have seen earnings boosted this year by strong overseas growth. As economist Joseph Carson told The Wall Street Journal recently, "The international influence on firms' profits has never been so strong."

Realizing this, other companies are investing heavily overseas -- Eli Lilly (NYSE:LLY) and Merck (NYSE:MRK), for instance, are increasing their presence in China, according to a PriceWaterhouseCoopers report.

Entrepreneurs and investors alike
Meanwhile, there are the master investors who have been buying up foreign stocks at a rapid clip. Davis Funds owns Chunghwa Telecom (NYSE:CHT) and Charles Brandes has been investing recently in Chunghwa, Brilliance China Automotive Holdings, and a number of other Asian businesses.

Even Warren Buffett stoked the international frenzy earlier in '06, with purchases of PetroChina and Israel's Iscar Metalworking.

The question we need to ask
So -- and you had to know I was coming around to this -- what have you been adding to your portfolio lately?

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This article was originally published on Jan. 19, 2007. It has been updated.

Tim Hanson owns shares of Wynn Resorts. Chunghwa Telecom and Eli Lilly are Income Investor selections. No Fool is too cool for disclosure.