Overwhelmed? Invest the easy way.

Like a car's suspension, your portfolio needs an occasional realignment. In fact, many advisers tell customers to take their investments in for a tuneup once or twice a year to make sure nothing is out of whack.

Nearing retirement? You might want to put more bucks in bonds. Watching the price of your favorite small stocks go through the roof? Maybe it's time to sell high and buy - well, you know the drill.

But not everyone has the money to hire a financial planner, let alone find the time to learn terms like "asset allocation," "portfolio beta score," and "equity risk premium." Enter "age-based" mutual funds, a growing investment niche for people who want to invest and forget.

If you plan to quit working in 2035, for example, a number of funds have been specially created to leave you ready for retirement in two decades. The fund's portfolio automatically adjusts, taking into account your investment needs each year.

"What we've done is designed this for folks as a core holding. You put the bulk of your retirement assets there," says John Sweeney, a senior vice president at Fidelity Investments, which offers 10 age-based funds. "We feel it will be a comfortable asset for people to have."

Plenty of customers agree. Age-based or "lifestyle" funds are becoming more common in workplace 401(k) plans, and they now make up about $25 billion of Fidelity's $903 billion in mutual-fund assets. While that may sound like a small piece of a large pie, it's twice the level of investment in the funds at the end of 2002.

Several other fund families also offer age-based funds, and the no-load index fund giant Vanguard began offering them last fall. In many cases, they are "funds of funds," meaning they're made up of a number of other mutual funds rather than stocks.

The Fidelity Freedom 2040 fund, for example, is made up of 13 stock funds and five bond funds. At the moment, bonds represent 10 percent of the fund's total investments. Like the other Freedom funds, that percentage will grow until the "target" retirement dates of 2038-2042 when it will reach about 80 percent (including short-term investments). Bonds are generally safer and less volatile than stocks, and experts say they should play a large role in the portfolios of most older people. That way, a stock market blowout won't devastate a senior citizen's nest egg.

In many cases, the returns on age-rated funds are hard to gauge because they're too new to have any long-term returns. Even if they have been around for a while, like the Fidelity funds, it's hard to figure out what to measure them against because they don't track specific sectors of the market like other mutual funds, says Kerry O'Boyle, a mutual-fund analyst at Morningstar.

One thing is clear, however: The funds invest conservatively.

"In general, they're just going to offer steady returns," Mr. O'Boyle says. "They're not going to break anyone's charts."

That's one reason why many financial advisers steer clear. "While these types of funds are really useful to people who are starting out and young, they might not be aggressive enough for them," says Lauren Klein, a certified financial planner in Irvine, Calif.

Then there's the one-size-fits-all nature of the funds. It's hard to predict exactly where you'll be in 20 or 30 years, and the funds don't allow for much flexibility compared with portfolios that allow you to engage in "slight tweaking to take advantage of opportunity," says Julie Schatz, a financial planner in Menlo Park, Calif.

Both Ms. Schatz and Ms. Klein say age-based funds can be useful for some people, however. Klein says they're an especially wise choice for those with less than $25,000 to invest. They can also be a good option for workers who don't have a lot of fund choices in their 401(k)s, she says.

If you do decide to buy into an age-based fund, O'Boyle of Morningstar recommends watching out for extra fees - some companies charge for the management of the included funds - and making sure you invest in a respected fund family. "Since these are funds of funds, you want a firm that has experience in lots of different areas of the market - large cap, small cap, international," he says. "There aren't that many shops that can provide the research and expertise in all of those areas."

If you're willing to take on more risk, O'Boyle recommends funds from T. Rowe Price, which invest more heavily in stocks. Vanguard is a good choice for more conservative investors, he says.

Just remember to ask yourself: "Who's making sure you're putting enough money in and being aggressive enough to get what you need?" Boyle says. If you don't trust your own judgment, professional money management provided by age-based funds may be a starting point on the road toward retirement.