Guillermo Vilas playing formidable and unflinching clay-court tennis, today won the Italian Open singles title that in years past had proved a particularly elusive prize for him.

Vilas buried 20-year-old Afro-Frenchman Yannick Noah, who was terribly nervous at the start of his first major tournament final, in the red dust of the Campo Centrale (center court) at Foro Italico. The scores were 6-0, 6-4, 6-4, and the 2-hour 6-minute match did not become interesting until Vilas was too far ahead to have his momentum thwarted.

Vilas, 27, had been in major finals a dozen times before, winning the Australian Open twice, the French, U.S. and South African opens and the Grand Prix Masters once each. He was composed, relaxed, determined and sharp.

"I had played here in the final before, and it was always so close, and I think every time I was a little bit unlucky," said the Argentinian left-hander, four times a semifinalist of at Foro Italico, runner-up to Adriano Panatta in four close sets in 1976 and to Vitas Gerulaitis in a five-hour, five-set classic last year. "This year, I was ready to win it."

Noah clearly was not ready. The engaging No. 1 player of France -- "discovered" as an 11-year-old in Cameroun by Arthur Ashe during a U.S. State Department tour through West Africa in 1971 -- had never reached even the quarterfinals of one of the major international championships. His inexperience was painfully evident as he lost the first eight games. "I think at the beginning he was kind of lost," said Vilas.

Normally a lithe and graceful 6-foot-4-inch panther, Noah was instead a big cat with rigor morits in thos first eight games. He had some good ideas for attacking Vilas, but his limbs were tight, his execution hesitant and indecisive.

He didn't hold serve for the first time and get his aggressive, explosive serve-and-volley game in harness until the third game of the second set. By then it was too late. Vilas was grooved, and never lost his serve in the match.

Finally settled in, Noah lost only five points in four service games to 4-5 in the second set. But Vilas held firm in the crucial 10th game, which he knew could mean the difference between a commanding two-set lead and a snowball-stopping loss of the second set.

Vilas played a strong game, putting five first serves in court and holding at 15. Thereafter he needed only one more service break for the match, and he got it in the ninth game of the third set -- drilling a forehand return winner off a second serve and forcing a volley error with a rocket backhand after Noah had double-faulted and muffed a volley for 0-30.

A sellout crowd of 9,000 spectators in a splash of joyous spring colors filled the white marble Campo Centrale on a hazy Roman Sunday. Italian sports audiences always choose a favorite so they can participate in the spectacle and today, in the absence of a native son, they were behind the newcomer Noah -- loudly and fervently, as is their wont.

Noah is an attractive player and personality. The son of a Camerounian father who played professional soccer in France and a French mother, he took up tennis in Cameroun, where there were only about two dozen courts.

After Ashe saw him and alerted French Tennis Federation officials, they brought Noah to Nice and enrolled him in their elaborate school and training program for promising juniors. He has developed into one of the emerging stars of European tennis, and a Great Black Hope.

But today, Noah obviously felt the burden of big match pressure.

Televised live throughout much of Western Europe -- including France, which is in the midst of a tennis boom -- and on tape to the United States, the match was fraught with commercial possibilities. Moreover, Noah is opening a 10-court club in Cameroun's capital of Yaounde this summer and hoping to spur tennis interest among native youngsters who have never been able to afford the game before.

At the start, he was tight as a drum. In the first game, he stayed back on this serve, pushing the ball, and won only one point. Instead of attacking, as he did later, he foolishly rallied with Vilas, then rushed his thrusts to the net.

Noah had break points in the second and fourth games, but both times Vilas whacked forehand approach shots and got out of trouble with decisive forehand volleys.

Playing steadily, and occasionally spectacularly, Vilas did not face another break point until the third set.

Noah should have been a relentless aggressor. Instead he engaged Vilas in baseline duels he could not win, and tried drop shots and dinks that Vilas covered every time. When he decided to go in, he frequently did so awkwardly, hurrying his approaches and leaving himself out of position and vulnerable. He was impatient, and hit an embarrassing number of volleys into the net.

By the middle of the second set, the crowd became more involved in a contest in the stands than the one on court. A couple of youngsters sent a paper airplane cruising across the court in midpoint, forcing a "let." Accusatory screams and gestures caused a commotion.

Five policemen made their way to the top of the arena and ejected three rowdies, but only after prolonged argument. The tournament director got on the public address system and appealed for order. One of the polizia cuffed an airplane-thrower as he escorted him out, drawing a mixture of cheers and boos. The dull match became secondary for five minutes because in passionate Rome, it seems, the only real crime is boredom.

Noah started to follow every serve to the net and to volley with more assurance, reforcusing attention on the court. But it was too late. He had one break point in the second game of the third set, netted an overanxious backhand, and ripped the commericial insignia off the right sleeve of his shirt in disgust. Vilas held, and lost only one more point on his serve until he was at triple match point.

Noah saved two match points with a volley and a mightly smash, but then Vilas hit a looping forehand crosscourt pass that clipped the sideline for a winner. He leaped into the air, battled a ball far over the stadium in jubilation, thrust his arms in the air, and cast an ear-to-ear grin at his coach, Ion Tiriac, in the stands.

This title meant a great deal to him, too -- much more than the difference between the $28,000 top prize and the $14,000 runner-up check. The Italian is the second most important tournament on the continent, behind the French Open, the unofficial world clay-court championship, which begins Monday in Paris. Vilas had been close Before, and he was indeed ready to win.

Vilas didn't lose a set in the tornament and conceded only 19 games in seven sets in routing Raul Ramirez, Eliot Teltscher and Noah in the last three rounds. Earlier this month he beat Bjorn Borg for the first time in more than four years, on clay in Duesseldorf, so he goes into the French and a likely semifinal meeting with Borg in a good frame of mind.