Investing can be a lonely business. If you use a full-service broker, you may or may not be happy with your broker's advice. If you use a discount broker, you won't get any advice at all. And if you try to do your own research, you're probably worried that you're missing something important.

On the theory that it's more fun to hang together than hang separately, there is the investment club. If riches are not guaranteed, there is, at least, a kind of camaraderie, a sense that "we're in this together -- win or lose."

Investment clubs come and go. Some are marvelously successful over a period of 10, 20, 30 and even 40 years. Others fall victim to bickering and disappointments when the market turns down or when members find that serious investing is too much work.

Thomas E. O'Hara, chairman of the National Association of Investors Corp. (NAIC), recalls that NAIC investment clubs reached an all-time peak in October 1970 of 14,101. But within 10 years, partly in response to declining markets, the number of clubs plummeted to 3,200. Since 1980, the roster of clubs has climbed to 6,000. NAIC counts 115,000 members.

If a club survives its first three years, says Murray Hamburg, president of the Metropolitan Washington Council of NAIC, the chances are it will last. Time does much to help build a club's portfolio.

If a club has 20 members putting in $20 a month, that's $400 a month, $4,800 a year and $14,400 after three years. Members have to be prepared to live with some losses and slow progress, but with that kind of nest egg, Hamburg says, the club will have the opportunity to show significant results from the growth stocks that are appropriate for NAIC investment clubs. Once members can take profits and reinvest them, he says, they will begin to see their holdings snowball.

Hamburg speaks from experience. A technical writer for MA/Com Linkabit Inc. in Vienna, Va., he has been active in NAIC clubs for 20 years, both here and in the New York area.

The Washington metropolitan area, Hamburg reports, has 157 clubs -- up from 102 clubs five years ago -- with about 2,500 members. Another 400 people are individual members of the NAIC, which is headquartered in Royal Oak, Mich. Individual members pay $27 a year in dues. Clubs pay $30 a year plus $6 for each member. All members receive the NAIC's monthly magazine, Better Investing, and a useful Investors Manual. For a small charge, members in this area can take a course in basic stock analysis one night a week for five weeks.

How do you join an NAIC club? Hamburg says NAIC rules prohibit it from publishing the list of clubs, although it does try to put prospective members in touch with clubs looking for members. Even so, he says, it may be easier for a would-be investor to start his or her own club by lining up friends and acquaintances. Clubs may not have more than 30 members -- most average 15.

To get in touch with NAIC, write the Metropolitan Washington Council, National Association of Investors Corp., P.O. Box 10231, Washington, D.C. 20018, or call (202) 387-1950.

In 1966, shortly after Elmon A. (Sunny) Miller retired from the U.S. Navy, the former pilot-turned-stockbroker got together with some of his old aviator pals and formed an investment club they called the High Fliers. At the start, their shares were worth $10 each. By the early 1970s, when the stock market was in the doldrums, their shares had declined to $4 each, and the 20 members decided to change the name of their club to the Flat Hatters, which is what they call pilots who fly at tree-top level. That's still the name of the club, even though the shares are now worth $33.35, and the contributions of $190,000 have become $540,000.

During his years as a broker, Miller said, he has worked with 50 to 60 investment clubs. He is still working with the Flat Hatters, even though the members long ago gave up their monthly investment meetings in favor of letting Miller handle their fund. His newest club is the Talboteers, 12 women who work at Talbots, a women's clothing store. Miller, a broker in the Washington office of Alex. Brown & Sons, works with his clubs, teaching the members about investments and how to analyze stocks.

Investment clubs help both investors and brokers, Miller noted. "I find members of investment clubs have better knowledge of the market than ordinary ciitzens," he observed. From the broker's standpoint, he said, clubs are a lot of work and brokers don't make much money on them, but the people a broker meets in the clubs often become clients -- and that helps make it worthwhile.

One of the major investment organizations operating in the Washington area is the American Association of Individual Investors (AAII). A national educational organization, it has 29 chapters around the country, including one that serves the Washington metropolitan area.

David Feigin, of Gaithersburg, a data processing consultant, who started the Washington chapter two years ago, counts 4,000 AAII members in the metro area, although 350 would be considered a heavy turnout when the local chapter has one of its four or five major program meetings each year. Scheduled for the future are dinner meetings on real estate investments, taxes, computerized investing and stocks. Recent meetings covered money managers, convertible bonds and other stock market strategies.

AAII membership costs $48 and includes a subscription to the organization's erudite monthly magazine, the AAII Journal. The articles are written by professional investors, academicians and other experts.

A recent Journal issue contained an interview with investment counselor Amy L. Domini, co-author with Peter D. Kinder of "Ethical Investing"; an article on "Neglected Stocks," by Avner Arbel, a professor of finance at Cornell University, and an article on investment strategy by Mark Hulbert of Washington, whose newsletter rates the performance of investment advisory newsletters. The tone of the magazine is serious, although the newer investor may find that some articles -- such as one on compound interest -- can be heavy going.

Feigin sees a growing interest in his organization. The average number of members attending meetings, he said, seems to be getting larger and the hard-core membership that comes to every meeting also seems to be growing. Feigin said that a basic rule is that AAII won't let investment advisers use the meetings at which they appear to sell their services.

Although the Washington chapter has subgroups that meet to talk about computerized investing and commodities -- and it may form one on mutual funds -- the one thing it doesn't have is an investment club. "I'm surprised no one is forming an investment club," said Feigin.

Investors interested in joining the AAII can write to the American Association of Individual Investors, 612 North Michigan Ave., Chicago, Ill., 60611, or call (312) 280-0170. Or they can contact the Washington chapter, AAII, P.O. Box 23687, Washington, D.C. 20026. Call (202) 387-6178 and leave a message.