James Stewart opened the front door of his Beverly Hills home, accompanied by a frisky, affectionate setter. Half expecting to confront the Jimmy Stewart I first grew fond of 30 years earlier in boyhood favorites like "The Stratton Story" and "Broken Arrow" (very stong sentimental influences, those two), I was mildly surprised to be greeted by this tall, cordial elderly gentleman who was slightly jowling and decidedly bald.

But the man at the door was not an imposter, merely Jimmy Stewart looking and acting his age, which will be 72 on May 20. Now in the 46th year of an impressive film career, he had just returned from location shooting in East Africa, a few weeks before receiving the American Film Institute's eighth annual Life Achievement Award. (The event was taped two weeks ago for a CBS special to be aired tonight at 9:30.)

A young woman appeared briefly at the top of a flight of stairs ascending from the wide foyer. She was introduced as Judy -- one of the Stewarts' twin daughters, born in 1951 -- before making a quick, smilling exit into an upstairs room. "Get a look at this," Stewart said, strolling into an antechamber dominated by a concert grand. He pointed to the exercise book on the piano stand, opened to a page of detached sixths. "Looks like something you'd get on one of those computers, some kind of coded printout," Stewart said. "You should hear her breeze through this stuff. I'd have about as much chance as -- well, might as well try to sight-read from a page of Greek."

Stweart did a little piano playing in "Anatomy of a Murder," as a sidelight to his role as the small-town lawyer. "My mother taught me to play five chords in the key of C," Stewart said. "Had a piano teacher for a while who liked to rap you on the knuckles with a ruler when you made a mistake. I found that kinda discouraging. But with those five chords in C, you can always fake it."

Growing up in Indiana, Pa. (Stewart's father ran a hardware store established by his father in 1853), the future movie star took to the accordion and continued with the sometimes dreaded instrument through prep school at Mercersburg Academy and college at Princeton, where he entered in 1928 expecting to major in civil engineering and graduated in 1932 with a B.S. in architecture. Simultaneously, he cultivated an intrest in amateur theatrics. Stewart became a fixture of Triangle Club productions at Princeton.

Stewart's remarkably natural acting skills evolved almost by accident. He agreed to join Joshua Logan's University Players on Cape Cod the summer after his graduation. Logan cast him a a chaffeur (with a single line, "Mrs. Belle Irving is going to be sore as hell") in a play called "Goodybye Again." Fortunately, the production was shifted to Broadway that fall. Stewart went along in is original bit role.

"Goodbye Again" eventually closed, but one thing and another extended Stewart's inadvertent Broadway career. By 1934 an unbroken string of small parts had led to the featured Broadway role in which Stewart first mad a big impression: Sgt. O'Hara in "Yellow Jack." His good friend Henry Fonda recalls seeing him later in "Divided by Three," in which Stewart had the role of Judtith Anderson's son.

"I remember wondering how the hell he got to be so good! I'd been at it for eight or nine years already, playing literally hundreds of parts of all kinds and really working at being an actor. And here was the skinny son-of-a-bitch who hadn't really tried very hard for maybe a year or so, and I'd just seen him do about the most moving job I've ever seen in the theater."

Stewart believes that "Yellow Jack" was the production that transformed him from a lucky amateur into a dedicated professional actor. "I think it became a conscious process then," he said, now settled on a couch in his study, where two walls are lined with bookshelves and a third with framed family photos and mementos. (The best-actor citation from the New York Film Critics for "Mr. Smith Goes to Washington" is there, along with a number of service awards and the honorable service citation mailed to the Stewarts after Lt. Ronald McLean, one of Gloria Stewart's two sons by her first marriage was killed in action in Vietnam in 1969.)

Of "Yellow Jack," Stewart recalled that "there were all these people putting forth just a tremendous effort to get it right. For the first time I thought, well, this is a craft, it's something that takes serious work and is worth working at.

"There was an excitement about the theater then, in the dead bottom of the Depression. The Broadway theater has never been as active as it was then. I think I was in about 35 plays, and I did nine plays in four months at one stretch, so you know they weren't all hits. But you acquired just a tremendous amount of training! It was wonderful experience. Looking back, I wish I'd had more of it."

In 1934 Stewart was cast in a two-reel Warners comedy that was shot on Long Island and evidently consigned to speedy obscurity. Fox tested him the following year but declined to offer him a contract. Finally, he was signed to a seven-year contract with MGM in the summer of 1935 after testing with Billy Grady, the studio's legendary talent scout and casting director.

Stewart made his debut at Metro in a courtroom melodrama called "The Murder Man," which starred Spencer Tracy. But in retrospect, it appears that while at Metro, Stewart got most of his big breaks on loan-out to other studios: at Universal, "Next Time We Love," the first of four movies in which he played opposite Margaret Sullavan, whom he already knew and respected as an earlier recruit of Josh Logan's at the University Players; at RKO, the George Stevens comedy "Vivacious Lady" with Ginger Rogers; at Columbia, the back-to-back Frank Capra hits "You Can't Take It With You" and "Mr. Smith Goes to Washington"; at United Artists in the martital soap opera "Made for Each Other" with Carole Lombard; back to Universal for the western "Destry Rides Again" with Marlene Detrich.

Stewart was an identifiable and ingratiating screen presence almost from the start, yet it took a quartet of pictures in the last months of 1939 and first months of 1940 to give him belated status as an MGM star: "It's a Wonderful World," a wacky detective comedy co-starring Claudette Colbert; Lubitsch's marvelous "Shop Around the Corner," which cemented the remarkably sensitive and pleasing chemistry between Stewart and Sullavan; Frank Borzage's anti-Nazi melodrama "The Mortal Storm," again with Sulvan; and George Cukor's sparkling production of "The Phildelphia Story," which brought Stewart his Academy Award.

"That was the game then," Stewart recalled. "I was a contract player. Must have been about 40 of us. Like a lot of folks, I ended up getting little parts in big pictures and big parts in little pictures. But I never went along with the stories you hear about MGM being this big, impersonal factory. All of the executives I knew at the studio were imaginatie people. They had judgment and, in a strange way, taste.

"It wasn't necessarily to my disadvantage to do a B at MGM and then be loaned out. I got to do a little thing with Maggie Sullavan at Universal because she'd been talking me up. That gave me a chance right away. I was traded to all the studios but you got that constant work and effort, with different people showing you the way. It was a 52-weeks-a-year thing. If you weren't in a picture or out on loan, you'd be working in a gym or doing a publicity shut or shooting tests with new leading ladies. Everything was just that much more training."

A healthy 32-year-old bachelor with no dependents, Stewart was the only major Hollywood actor who ranked high on the draft lottery list. With induction only a matter of time, he tried to enlist in January of 1941 but was turned down because his 147 pounds was under the minimum required for men his height, 6-foot-3. After gorging himselfs on carbohydrates for a few weeks, he applied again and was accepted. He was inducted on March 22 1941, less than a month after accepting his Oscar.

Stewart kept a low profile during his wartime service, and it's easy to forget that he entered before any other star, stayed the longest and compiled the most distinguished record. An aviation enthusiast from boyhood and an experienced pilot when he was sworn in as an Army private, Stewart was immediately accepted for Air Force training. He won his wings in August 1942 and instructed bombadier cadets until November 1943, when he went to England as a B-24 squadron leader attached to the Eigth Air Force. He flew 20 bombing missions over Germany as either a squadron leader, wing commander or operations chief before V-E day.

Stewart returned to the States in September 1945 with the rank of colonel and several decorations: the Air Medal, the Distinguished Flying Cross with Oak Leaf Cluster, the Croix de Guerre with Palm, seven battle stars. He remained in the Air Force reserve until 1968. President Eisenhower appointed him a brigadier general in the reserves in 1959, after Sen. Margaret Chase Smith, herself a reserve officer, had blocked the appointment for two years on the grounds that Stewart had not put in the required reserve training.

After the war Stewart was keenly apprehensive about his acting career when returning to Hollywood and grateful that Frank Capar's "It's a Wonderful Life" materialized as soon as it did. "It's a favorite of mine," he said. "Looking at it now, I'm sorta proud of it, and it was tremendous good fortune to get a part like that just after the war."

Many people believe that Stewart's Oscar for "The Philadelphia Story" was clinched by his failure to win the year before the emotionally gaudier role of Mr. Smith is one of the rare Stewart performances that can begin to rub you the wrong way. It stereotyped his screen image permanently. Surely the most familiar Stewart still is the image of the exhausted, disillisioned Jefferson Smith at the end of his desperate filibuster -- a cruelly exploited idealist, the symbol of innocence abused.

Stewart is an exceptional interpreter of suffering, but I much prefer the mature, ambivalent portraits of decent men in his postwar vehicles who find themselves profoundly disillusioned or frustrated. The most impressive example remains his distraught small-town do-gooder, George Bailey, in Capra's "It's a Wonderful Life." An extravagant Christmas tearjerker of 1946, it was the first project for both men after they returned from both men after they returned from military service. No matter how sentimental Capra's story calucations become -- and they become almost ruthless -- Stewart's sensibility rises to the challenge of clarifying every conflicting emotion warring within the protagonest. It's a phenomenal performance: always vivid, eerily authentic, unpredictably inventive and touching. The movie was not a hit when it was first released, but it's a durable, vigorous Capara indiscretion, and Stewart's performance really stands the test of time. The longer you're a family man, the more authentic it begins to seem.

Stewart didn't become a family man until his marriage in 1949, but he's got Bailey's raging mixed emotions beautifully distilled. This powerful sense of identification with emotionally complex and troubled men may have grown out of his wartime service, perhaps from sheer proximity to stress, fear and endurance. The same awareness is evident in Stewart's characters drawn from real live in modest postwar biographical melodramas like "Call Northside 777," "The Stratton Story" and "Carbine Williams," in the extraordinarily grittyh series of Westerns he made in collaboration with the late director Anthony Mann (they began in 1950 with "Winchester '73" and concluded in 1957 with "Night Passage"), and in his performances for Alfred Hitchcock as the vulnerable, obsessed truth-seekers of "Rear Window" and "Vertigo."

After the war, Stewart recalled, "The great thing was to get back in the thing and pick up where you left off Not have to break in all over again. There was a lotta uncertainty. And then this strong role just kinda grew out of a short little theme, something like 'Nobody's born to be a failure after Frank and the writers jumped on it. The thing just worked. Freank deserves all the credit, of course. He was so good at keeping a pace. Once he got a story started, it just didn't stop."

Stewart said he is "convinced there's a mystery to this business which has always been a tremendous asset. So ofter little things, little looks, can make so much difference. I never realized till I'd been in the business 20 years -- more than that -- how important tiny little moments are to an audience. All of them might have happened by accident: a look, a pause, a turn. It's the audience, the audience is the one who discovers it.

"People will say to me, "I've seen a lot of your picture shows, but the one I like best, you're in this room, and you did such-and-such, and I thought that was such a nice thing, you remember that?' And I always do. Sure enough, I know exactly the spot. Nine times out of 10 you realize it was a little thing you did that worked, and you felt it too. When you think about it, it's a number of those things that add to the effectiveness."

A number of those things achieved frequently and sustained over time add up to a career as distinguished and respected as Stewart's. Not that Stewart seemed to be looking back. He was enthusiastic about the African project, called "Bloddy Ivory." Stewart hopes it will register as "really a stong indictment of the international poaching racket, which is a very destructive thing. The animals are on their way out, they're literally dying out, and it's strictly a dollars-and-cents evil. Ivory brings $200 a pound, and the game reserves are too vast to police adequately."

Stewart had just received a photo of himself in a scene from "Bloody Ivory." The film company wanted his approval to use it for advertising purposes. It showed Stewart playing with a spider monkey, but the camera position made it vertually impossible to recognize the bearded actor. Stewart, who had just shorn the beard a few days earlier and complained that "I still don't know what to do with my hands -- they keep wanting to stroke and scratch the thing," felt he'd have to insist on another picture.

"You see what I mean? From that distance you can't tell who that old-timer is. After all, I havaen't kept at things this long just so I can cause people confusion."