Investing in emerging markets usually means having to accept higher risks and uncertainties than in developed countries. However, some emerging-market companies can provide exceptional long-term growth opportunities for your portfolio. MercadoLibre (NASDAQ:MELI), Melco Crown (NASDAQ:MLCO), and Baidu (NASDAQ:BIDU) are strongly positioned for growth for years to come.

Investing in a free market
MercadoLibre means "free market" in Spanish, but the company is better known among investors as "the eBay of Latin America." There are valid reasons for this -- with nearly 18% ownership, eBay is a major shareholder in MercadoLibre, and both companies have similar business models.

In addition to being the leading e-commerce platform in Latin America, MercadoPago does for MercadoLibre what PayPal does for eBay: It is a payment method that has been expanding beyond the platform and growing as a stand-alone business on its own merits. Just like eBay, MercadoLibre has been growing into other areas, like advertising, classifieds, and technological solutions for its clients.

The company has produced outstanding growth for investors over the years; sales have increased at 34.4% annually through the last five years, while earnings have grown at an even faster 59.9% per year through that period. MercadoLibre continued performing strongly last quarter: Revenues in local currencies grew by 45%, and sales in U.S. dollars increased by 27% during the third quarter of 2013.

On the other hand, economic risks could present serious headwinds for MercadoLibre in the medium term, especially when it comes to Argentina and Venezuela, which represent 27% and 19% of revenue, respectively. Both countries are going through serious economic uncertainties, including capital control regimens, currency devaluations and rampant inflation. This could have a material negative impact on the company's financial figures when translated to U.S. dollars.

This casino is no gamble
Melco Crown is one of only six companies granted concessions or sub-concessions to operate casinos in Macau, the only region in China with legalized gambling. Macau has been booming recently, and, judging from recent statistics, there is no slowdown in sight: According to Macau's Gaming Inspection and Coordination Bureau, gaming revenues for the companies operating in the region increased by 18.6% to $45.2 billion in 2013.

The company has benefited enormously from growing gaming demand in Macau. Sales have risen by more than 45% annually in the last three years, and numbers for the last quarter remain remarkably strong, with a 24% increase in revenue during the third quarter of 2013.

Competition remains under control due to the limited amount of land available to build new properties and government reluctance to issue gaming licenses because of social and political considerations. Melco Crown is also expanding into the Philippines and exploring opportunities in Japan, so growth prospects are looking quite strong for the company in the medium term.

Investing for growth in China
Baidu is the leading Chinese language Internet search provider. The company makes most of its sales by providing online advertising through an auction-based pay-for-performance service mostly targeted to small and medium-size businesses. Baidu is also performing strongly in mobile and investing heavily in powerful trends like video, maps, and travel services, among others.

China is a risky country for investors, and the Internet sector is particularly exposed to regulatory uncertainties, technological change, and a dynamic competitive landscape. But there is no denying that Baidu is capitalizing its opportunities and delivering extraordinary growth rates for shareholders.

Revenues have increased 66.5% annually through the last five years, and the company reported a big jump of 42.3% in sales for the third quarter of 2013. Earnings per share were up by only 1.3% during the quarter because of big spending in several growth areas, though.  

Considering the huge opportunities the company has ahead of it in the coming years, Baidu is doing the right thing by prioritizing growth and expansion at the expense of short-term profit margins -- even if that can be a source of added uncertainty for investors in the company.

Bottom line
Investing in emerging markets is not for the faint of heart; these companies are relatively more obscure and harder to analyze than well-known U.S. businesses. Besides, political, regulatory, and economic uncertainties tend to be considerably higher in those countries. However, exceptional growth opportunities can more than compensate for risks when you invest in the right names.