Q. Our son, Jim, turned 3 in March. He is the oldest of two. Our second child, a daughter, was born in November.

Jim started talking at an early age. His vocabulary is very good, and he has put together complete sentences for some time. About the time he was 2, he started stuttering. He only stutters when he is excited, upset or tired. He plays well with other kids, and so far as we know does not stutter with them.

We try to keep Jim from getting too excited when he is talking, and we try to have him speak slowly. We do not finish sentences for him, nor do we make light of his problem.

What can my wife and I do to stop this problem early? Is it too soon to think about a speech therapist?

A. Sometimes it seems as if there are almost as many theories about stuttering as there are stutterers (and there are 2 million in the United States alone).

All preschoolers go through some "disfluency," as it's called, perhaps repeating a word several times. It's only when there is difficulty with a particular sound or a "part-word" that you have true stuttering. Even then, it has many patterns to it; nature is always complex.

One-half to two-thirds of these true stutterers recover spontaneously without any outside help at all; the others usually can overcome it with early treatment. If therapy is postponed, the problem is often curbed, but seldom cured. Nevertheless, stutterers are fluent about 95 percent of the time.

As you've noticed with your son, stuttering is situational. Stutterers can sing; usually read in unison; often act on the stage or play with friends or their pets without any hesitations, only to stammer at certain times and places and often with the people whose opinion matters most to them--like parents or teachers or both--especially if they are troubled by the impediment.

It's hard not to be troubled. Hardly any other handicap involves others as intimately as stuttering. The audience hangs on every word and when it comes to their children, parents are the best word-hangers of all.

This makes some experts think a stutterer's parents are perfectionists, at least in the eyes of the child. They may not make excessive demands, but it's thought that their expectations are too high for that particular child at that particular time. The more they react to his stuttering, the more the child reacts to their anxiety. This may be why some studies show that stuttering--which affects boys four times more frequently than girls--is more likely if parents are used to achievements, or are working hard to move upward.

According to Dr. James Lingwell of the American Speech-Language-Hearing Association, stuttering is not one disorder but many, which may be why there are so many conflicting theories. It may come from a neurological basis, a psychological one or perhaps an allergic one, or it may occur because of faulty learning or poor rhythmic control. Or it may be a combination of some or all of these sources.

The treatments are different, but basically they are psychotherapy and behavior modification. Most speech-language pathologists (the new name for speech therapists) combine the two techniques to some extent.

In behavior modification, pathologists teach a child to monitor his own speech, so he can be more fluent. They may reshape speech patterns, the method used at Kean College, Union, N.J. Or they may teach very slow speech with biofeedback, to monitor the throat muscles that may block when stuttering, the technique used with much acclaim at the Communications Research Institute at Hollins College, Roanoke, Va.

Although Freud found psychotherapy didn't work for stutterers, a small but vocal group considers it a psychological problem and treats the disorder with hypnosis; drug therapy; desensitization--by gradually helping the patient face his anxiety--and by helping him talk about his feelings.

Philip Glasner, emeritus professor of pediatrics and psychiatry at Johns Hopkins, treats it as a family problem, working with the child and his parents. Although his psychological emphasis is quite controversial, most pathologists now agree with him that early treatment is the key.

That's why you're wise to consider intervention now. You don't want the patterns to become ingrained, or for Jim to suffer unnecessarily.

And suffer he will. The pounding, the shaking, the sweating--the inability to focus sometimes--are terrifying prospects for the stutterer: The fear is always there. If a child didn't have a psychological problem before, it's quite likely that stuttering might cause one.

First you need an evaluation from a speech pathologist to find out if your child is a true stutterer. Even though he has a good chance of outgrowing the disorder, this appraisal--which may take several sessions--will make you rest easier. And that in turn, will make him less self-conscious when he talks with you.

You also will learn how to deal with his stutter better: to make eye-to-eye contact when you talk; to be as patient as you can; to listen to what your child says, and not how he says it.

Unless the pathologist is extremely sensitive and trained to handle the interplay in a family, however, you also may want to meet with a psychotherapist to uncover any stress that might cause the stuttering. A new book, Childstress! by Mary Susan Miller (Doubleday, $14.95) also may help you realize how much a child feels, and how hard it is for him to talk about it.

Whether you choose a pathologist or a psychologist or both, you'll want to place your little boy with someone who likes children and has worked with them often, who has helped many stutterers before--and therefore has much clinical experience--and someone your little boy likes.

Questions may be sent to Parents' Almanac, Style Plus, The Washington Post.