The Bespoke Investment Group released its year-to-date chart of stock market performance by country last week, and the results may surprise you. When you think of countries with the best performing stock markets, Sri Lanka, Bangladesh, Estonia, Lithuania, and the Philippines probably don't leap to mind. Overall, the regions dominating the list are Southeast Asia, Eastern Europe, South America, and Africa -- regions that mostly do not include developed or even emerging market countries. But what if you want to get in on that action? Unfortunately, investing in "frontier markets" is as difficult as the name implies.

There is no official definition for the term, but generally frontier markets are different from emerging or developed markets in that they tend to be either extremely small, recently opened to foreign investors, or simply less economically developed than emerging markets. Each of these factors helps explain the extreme performance in these markets. Larger markets have more companies weighing down averages, new markets can attract an initial burst of investing, and less-developed markets have more room to grow.

However, those same factors make frontier markets difficult to access. An investor wanting broad U.S. exposure could buy one of the dozens of S&P 500 index ETFs, but there is no index ETF for a country like Sri Lanka. Similarly, if a frontier country's individual companies have shares listed on foreign exchanges at all, they tend to only be listed on the London or Luxembourg stock exchanges.

The good news is that there are a few exchange-traded funds that track frontier markets generally, such as the Guggenheim Frontier Markets ETF (NYSE: FRN), or region-specific ETFs such as the Market Vectors Africa ETF (NYSE: AFK). Some brokers such as Interactive Brokers (Nasdaq: IBKR) also offer access to foreign exchanges like the LSE, allowing an investor to invest in individual frontier companies.

The simplest solution, though, is to find multinational corporations that have expanded into frontier markets. Wal-Mart (NYSE: WMT), for example, recently made its biggest acquisition in a decade, buying Massmart Holdings, one of the biggest chain stores in Africa, operating in 13 countries. Similarly, in 2009, McDonald's (NYSE: MCD) collected 19% of its revenues from APMEA (Asia/Pacific, Middle East, and Africa) countries.

Frontier markets are like the Old West, in that they offer many opportunities, but not without some extra effort. It takes a kind of investing cowboy or cowgirl to take on the extra risks and go out on the edge to access these countries.

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Fool contributor Jacob Roche holds no position in any of the companies or funds mentioned. Wal-Mart Stores is a Motley Fool Inside Value recommendation. Interactive Brokers Group is a Motley Fool Stock Advisor pick. Wal-Mart Stores is a Motley Fool Global Gains recommendation. The Fool owns shares of Interactive Brokers Group and Wal-Mart Stores. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.