What do the Aden sisters, in their Costa Rican perch, see for gold these days?

It may seem like just another residential home on a quiet, tree-lined street outside the Costa Rican capital of San Jose, but once you step across the threshold into its chart-filled rooms, view the high-tech communications equipment, and talk with its bilingual staff, you know you're in the world of high finance.

This is Aden Research, a small but thriving company that specializes in forecasting the price swings of gold and other precious metals by way of its newsletter, the Aden Analysis. Its founders and chief analysts, California-born sisters Mary Anne and Pamela, are half American, half Costa Rican, and in their mid-30s. Although young by industry standards and relatively new to the game - they began forecasting in 1976 - the Adens have won a large and loyal following (15,000 subscribers to date), along with a reputation as astute prognosticators of major gold market turns.

''The beauty of this work,'' explains Mary Anne, leading a visitor on a guided tour of the spacious Spanish-style house, ''is that you can live just about anywhere on the globe as long as you're connected to the markets.''

In fact, the Adens are internationally well connected. Adjoining the sparsely furnished living and dining room areas which serve as their offices is an efficient communications center. It's filled with computer terminals, television consoles, a telex and a Reuters wire, linking their financial outpost directly with the major gold markets in New York and London and providing the latest updates in world business news.

But the most impressive aspect of the Adens' operation is the sheer volume of charts found scattered throughout their workplace. One former bedroom, bare of furnishings, is given over to charts tracing the movements of major currencies such as the Japanese yen and the Swiss franc, while another room tracks the ups and downs of worldwide gold and interest rates. A hall linking the two rooms is reserved for the Latin American currencies, another for the stock market and economic indicators. All told, the Adens make daily, weekly, and monthly updates on more than 300 charts.

''We keep all these charts,'' explains Mary Anne, ''to help us forecast where prices are going on a monthly basis for our readers. We also use them to do correlation studies to find out what leads and what lags in the economy. It's fascinating, because you might find that something you never dreamed of will help you in figuring out where gold prices are going, factors like the deficit, the index of economic indicators, consumer spending, and household borrowing. Major turns in a lot of these indicators will consistently lead gold by a couple of years.''

What the Adens currently see in their charts, they say, indicates that gold is once again poised for an upward move, and this one promises to be more volatile and extreme than the two major cycles they accurately predicted in the past. In late 1976, for example, with gold trading at about $130 an ounce, the Adens announced that it was moving into a bullish trend. Then in 1978, with gold at about $200, they predicted its rise within a two-year period to $700 or $800. Gold reached $850 in January 1980. Later that year, the sisters asserted that it would plunge to around $300 by mid-1982. It did just that in June of that year.

(In 1982, the Adens told the Monitor that gold was beginning a 31/2-year bull market that would peak at $4,000 an ounce. So far that has been far from the case, with gold prices actually weakening. But they still forecast that gold will shoot up to $4,000 by 1986 or '87.)

Pamela notes: ''We're not real stubborn about that price - and it's been so overquoted. The point is that if it hits the $2,000 mark and our indicators show it's coming down, we would issue sell signals, but it looks like it's going to much, much higher levels.''

To understand the reasoning behind their projections, look to the federal budget deficits, the sisters say. ''In a nutshell,'' explains Pamela, ''that's the cause. A growing deficit forces an increase in the money supply and the effect is high levels of inflation and rising gold prices because gold always tends to anticipate and rise with inflation.''

The Adens admit they had expected gold to make its move by the middle of last year. ''We called the major bottom for between March and July of 1982,'' notes Mary Anne, ''but the lull was longer than we expected and during that time in our newsletter we were still recommending that people buy even when gold moved to $400 and $500.'' Still, the Adens make no apology for that advice, because, they insist, gold's major trend is up and will continue in that direction over the long haul.

''If you look at gold just since it started to trade on the free market back in 1968, it's gone from $35 to $400 an ounce,'' continues Mary Anne. ''Besides, we've always tried to impress on our readers and others that we've never claimed to be short-term projectors. We're advising people to buy and hold for the long term - in this case for the next three years. But even if they hold it for 20 years they'll be fine.''

Who should be investing in gold? According to the Adens, both the big and small investor, and that includes the average person with little savings and few economic resources. ''Eventually those will be the people hurt most by inflation ,'' maintains Pamela. ''Those are the people who most definitely should be buying, even if it means a few silver and gold coins.''

For the small investor, the sisters recommend the South African Krugerrand or the Canadian Maple Leaf, because they are difficult to counterfeit and easy to liquidate. Buy from a reputable dealer, they caution, and personally supervise the storage.

The Adens, both married and raising families in San Jose, now consider Costa Rica their permanent home base. They agree that the vacation that brought them here from their jobs at a Long Beach, Calif., loan company back in 1974 profoundly changed their lives. Instead of returning home, they began an apprenticeship with a private gold speculator, which led to a job in research development with a Costa Rican investment firm.

For the Adens, Costa Rica provides professional and personal appeal. Explains Mary Anne, ''We're so much in the habit of doing our work in this type of environment, just the two of us talking back and forth about the markets. We're not swayed by too many outside people and we've found that that works better for us.''

Nonetheless, the Adens do worry about the growing turmoil in Central America, especially neighboring Nicaragua. Although at present it shows no sign of spilling over the borders, they say they plan to keep a close eye on it, just like the gold markets.