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

Why? Because at the time, the Wynn Macau -- Wynn's latest megacasino -- was just 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
And how has the Wynn Macau fared? Quite well -- though the stock has dropped as competition has heated up in Macau.

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 Anheuser-Busch (NYSE: BUD), which owns and operates the Wuhan and Harbin breweries in China and owns 27% of Tsingtao Brewery. It also recently started importing its Grupo Modelo brands to the country. And don't forget Yum! Brands (NYSE: YUM), which is expending significant capital to start East Dawning, the firm's attempt at the first successful nationwide fast-food chain in China.

Entrepreneurs and investors alike
Then there are the master investors who had been buying up Chinese stocks at a rapid clip. Ruane Cunniff once had a stake in TOM Online, Ron Baron a stake in New Oriental Education (NYSE: EDU), and John Keeley shares of Home Inns (Nasdaq: HMIN).

Even Warren Buffett has stoked the international frenzy in recent years, with purchases of PetroChina (NYSE: PTR) and Israel's Iscar Metalworking.

The interesting point today is that all of these investors have since sold their shares of China stocks. That development underscores an important caveat about investing in China: You must pay attention to valuation. These are exciting stocks with great prospects, but even the best companies can become bad investments if you pay too much.

The good news is that thanks to recent market volatility, the prices of each of these companies have been dropping.

The question we have to ask
So -- and you had to know I was coming around to this -- have you been taking advantage and adding international stocks to your portfolio?

If you're looking to do just that, one place I'm set to start is at our Global Gains international investing service. You can see our top stocks for new money now as well as our picks from our research trips to Asia and Latin America by joining free for 30 days. Just click right here.

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

Tim Hanson owns shares of Wynn Resorts. TOM Online is a Motley Fool Stock Advisor pick. New Oriental Education is a Global Gains selection. Anheuser-Busch is an Inside Value choice. No Fool is too cool for disclosure.