A NUMBER of years ago when he was just discovering wine, a friend of mine purchased a famous old burgundy to serve me for dinner. It had already been opened and decanted when I arrived. But when we tasted the wine, we found it lacked fruit and had very little bouquet --a disappointment, I said, and not at all typical of that producer's wine. Then my host told me he had opened it the night before because he thought that breathing was good for a wine.

My friend, wiser now, has never forgotten his expensive lesson. Allowing an old wine to breathe too much has probably ruined more fine old wines than any careless winemaker.

In fact, breathing is one of the most hotly debated subjects among wine aficionados. In wine jargon, breathing is the opening of a bottle of wine between 15 minutes and several hours prior to drinking. The presumed purpose of this ritual is to permit the wine to develop complexity or, as wine enthusiasts say, "open up."

Over the last several years, two schools of thought have debated whether breathing is necessary. One side takes the position that opening a bottle of wine an hour or more in advance of drinking it is ridiculous, and hazardous to the wine's freshness and fruity bouquet, not to mention its taste. The other school wholeheartedly endorses breathing a bottle of wine, claiming that this process softens the wine and permits it to develop complex nuances in its bouquet and flavor.

It is absolutely unnecessary to breathe or decant a white wine, unless you want to show off a decanter. Most of a white wine's appeal is its freshness and crisp, fruity flavors--all of which will deteriorate rapidly with prolonged exposure to air. Consequently, breathing is restricted to red wines.

Breathing can be as simple as pulling a cork from a bottle and leaving it to stand 30 minutes or more before serving. Most observers, however, feel that this particular type of breathing serves little purpose, as the amount of air passing through the neck of a bottle is negligible. Real breathing only occurs when a wine is decanted. All old red wines that have deposited a sediment are decanted, primarily in order to separate the clear, brilliant wine from the coarse-tasting, cloudy deposits. The act of decanting significantly aerates the wines. For those who subscribe to breathing wines, decantation is a mandatory preparatory step to the serving of red wine whether it is young or old.

I have experimented with wine breathing for some time, and have come to the conclusion that breathing wine is really a trade-off. Yet certain patterns have emerged, and I believe there are valid guidelines on the subject.

Breathing of red wine should be considered only for big, rich, tannic wines. This excludes most all the world's red wine production, except the so-called collector's or serious enthusiast's wines such as French burgundies, rho nes and bordeaux; the big Italian red wines from Piedmont and Tuscany; as well as the big red wines of California, such as cabernet sauvignon, pinot noir, zinfandel and petite sirah.

With regard to bordeaux, I have generally found that the big tannic vintages like 1978, 1975, 1970 and 1966 generally develop subtle complexities in their bouquet after 15 to 30 minutes in a decanter. They also give the impression of rounding out or softening, as followers of the breathing school maintain. But after about 30 minutes, there is a slight loss in the fresh, fruity intensity of the bouquet.

As for lightweight, less powerfully constituted wines, which are subtle and fruity already--for example, the 1979, 1976 or 1967 bordeaux--most of their charm is their fresh, lively, vibrant fruitiness. Such quality seems to suffer significantly from extended breathing; such wines, instead of developing, take on a bland, dumb, unfocused aroma and taste.

With old bordeaux, 10 to 15 years of age or older, I believe that decanting, simply to avoid the sediment which has fallen to the bottom of the wine bottle, is necessary. However, such old wines should never be left for extended breathing unless you are intimately familiar with the specific wine. An old wine may evolve and improve for several hours in an open decenter, but more often than not, it will oxidize quickly, losing much of its bouquet and fruitiness. Once that has passed away, it cannot be resuscitated.

The rules for bordeaux are not applicable to French burgundy. The great majority of today's burgundies are generally made in a very soft, supple style, requiring little cellaring for them to reach maturity. Furthermore, most modern-day burgundies, when mature, don't seem to last very long at their plateau. In short, their decline can be astonishingly rapid. In tasting burgundies, it is very rare to find a wine that improves with breathing. While some burgundies require decantation because of sediment, the process of decanting alone is enough aeration for today's burgundies.

As for California's big red wines, I have never been a believer that California cabernet sauvignon, zinfandel, pinot noir and petit sirah improve with breathing. These wines, because of a number of factors, are made in a style that is rich and intensely fruity and usually quite full bodied. Such wines almost always taste their best when just opened. But the biggest and most tannic of such wines do indeed soften if left to breathe for an hour or more. This does not, however, offset the loss in their rich, fruity intensity in aroma and flavor.

What conclusions can one reach? If you value the fresh, intense aroma and character of the grape from which the wine was made, then breathing will only prove hazardous to your enjoyment of the wine. If you prefer the feel of a softer wine on your palate with a less obvious bouquet, then breathing may very well help. Certainly, the observations I have made are general guidelines, and there are exceptions. But do remember that breathing is certainly not recommended for young, fresh, light-bodied red wines and certainly does nothing to improve white wines. If you stick to giving 20 to 30 minutes of breathing to big, rich, tannic red wines, then you are usually on safe ground.

Lastly, wines that are older than 10 years are best given their breathing in the glass in front of you. You can then decide whether the wine is best drunk up, or swirled and coaxed around in the glass in the hope that more interesting scents and flavors will emerge.