When you look at your retirement portfolio, what do you see?

Chances are, you see what most folks see: a mix of stocks and mutual funds, with the funds covering a range of categories from U.S. stock indexes to fixed-income investments of various types.

But do you see anything outside of the U.S. markets? If not, that's understandable. Investing outside of the U.S. carries with it a whole new set of challenges, ranging from different financial reporting requirements to language barriers to the need to understand the interplay of various currencies.

But there are compelling reasons to get past those challenges. Like it or not, globalization is a rapidly moving reality. Countries like India and China and Brazil will offer extremely rapid growth -- and thousands upon thousands of new businesses -- in the coming years. If you're building a portfolio for the long haul -- specifically, for retirement -- can you afford not to have international exposure?

I think it's really important. I also think that getting it doesn't have to be complicated.

The challenges of global investing
Many investors are daunted by the idea of investing in non-U.S. stocks. It's hard enough to do research on domestic companies that are listed on the major stock exchanges, meet strict U.S. reporting requirements, and have all of their financial reports and key statistics available on Yahoo! for the price of a few mouse clicks.

On top of that, when you invest outside of the U.S., you might have to consider currency fluctuations, operations dependent on markets and cultural environments you may have never seen firsthand, different reporting requirements, the potential difficulty of getting audited financial statements, and language barriers, among other factors. Unless you stick to big global companies that are active in the United States like BP (NYSE:BP), Nokia (NYSE:NOK), or Novartis (NYSE:NVS), you may not be able to get firsthand exposure to a foreign company's products or services without expensive plane tickets. It's hard to "buy what you know" in such circumstances.

Of course, buying what you know is a limited strategy. The real key to successful stock investing is to focus on buying what others don't know. And although there are stocks like Chinese online gaming leader The9 (NASDAQ:NCTY) and Macau's Nam Tai Electronics (NYSE:NTE) that are both promising growth stories and listed on U.S. exchanges, the real growth is in stocks that aren't listed here yet -- the stocks that are really unknown, at least in the U.S.

For most retirement investors, that level of research is just not realistic. Fortunately, we have a backup plan.

An easier way to go abroad
When it comes to retirement investing, I'm strongly in favor of low-effort, high-return strategies, at least for the bulk of your portfolio. Sure, we're unlikely to land too many 20-baggers that way, but this is money we're going to need to live on someday. We want growth, and we're willing to takesome risk, but we can't afford huge wealth-killing mistakes.

Of course, the lowest-effort strategy is to just buy an index fund. That's certainly better than nothing -- we'll get some exposure that way, and we won't lag the market. But, as the Fool's Rule Your Retirement newsletter has repeatedly argued, this is a case where hiring professional help -- via actively managed mutual funds -- deserves serious consideration.

Take something like the Fidelity International Small Cap Fund (FISMX). It's not a superstar -- just three Morningstar stars -- but it's a fairly solid performer, beating the benchmark EAFE Small Cap Index by 3% or more over most periods.

Its big holdings include companies you might not have heard of, like British pay-television innovators NDS Group (NASDAQ:NNDS), Danish wind turbine leaders Vestas Wind Systems … and a whole bunch of others that aren't listed on U.S. exchanges and are unknown to most American investors. See my point?

Making it happen now
If you haven't already, take a look at the international funds available in your 401(k) plan. Assuming you're more than 10 years from retirement, allocating about 25% of your portfolio to international stocks is a reasonable starting point. You should have some exposure to emerging markets and small caps, as well as a core of more established stocks.

Still not sure where to start? Take a look at Rule Your Retirement's Asset Focus section, under the Resources tab. (It's a paid service, but a free trial gives you full access for 30 days.) There you'll find complete detailed guidance for building out the international corner of your portfolio. You'll also find a list of recommended funds, some of which are likely to be in your plan. But no matter how you decide to go global, do it soon -- this down market isn't going to last forever.

Fool contributor John Rosevear has no position in any of the companies mentioned. Nam Tai is a Global Gains recommendation. Morningstar is a Stock Advisor recommendation, and the Fool owns shares of it. Try any of our Foolish newsletter services free for 30 days. The Fool's disclosure policy is a big fan of globetrotting, with or without the Washington Generals.