If you have examined the results of Middle Atlantic tennis tournaments the past three years, you will undoubtedly recognize the name. In this part of the world, it is difficult not to notice a name as distinctive as El Motaz Sonbol.

Sonbol is a native of Alexandria - not the suburban Virginia community but the second-largest city in Egypt. As first secretary of the commercial and economic office of the Egyptian Embassy here, he is currently in the final year of a four-year U.S. assignment that may be extended.

Local tournament players hope so because "El Motaz," as most of them call him - using his full, formal first name - has become a prominent part of the area tennis scene.

An extremely fit and steady player at age 41, he won the Middle States men's singles title in 1976 and is currently No. 1 in the Greater Washington Area rankings.

He was clobbered last night, though in the semifinals of the $1,300 Gus Castillo-U.S. Professional Tennis Association tournament at Indian Spring Country Club in Silver Spring. Englishman Graham Stilwell, a former world class player who is now the tennis director at Skyline Racquet & Health Club in Falls Church, beat him, 6-2, 6-0.

Stilwell will play George Amaya (6-1, 6-2 winner over Skip Bishop) for the $400 first prize in singles todat at 3 p.m.

The Castillo tournament is named for the popular, 36-year-old pro at Indian Spring, a former Davis Cup player for Colombia (1963-64). He advanced the prize money against entry fees. The tournament attracted 76 of the area's best amateurs and teaching pros.

In another place and time, the Stilwell-Sonbol match might have been place in an early round of the Davis Cup, Egypt vs. Great Britain.

Sonbol was a member of Egypt's national team from 1959 through 1974, when he came to the U.S. He was on the Davis Cup team many of those years, usually playing No. 2 behind Ismail El Shafei, his country's bestknown player. he played internationally in the '60s and early '70s, winning small tournaments in Greece, Cypress and Kenya.

Stilwell, 32, was a surprise selection to play Davis Cup singles for Britain in 1969 because he was unranked in his native country, having been sidelined with an arm injury in 1968. But he had a spectacular season, winning 10 of 12 cup singles matches to lead Britain to the interzone finals, its furthest advance since relinquishing the cup to the United States in 1937.

He had other notable victories that year (Fred Stolle, Manuel Santana, Zeljko Franulovic, El Shafei), and earned a contract with World Championship Tennis. Never a consistent winner in five seasons with WCT, he had scattered "good wins," including one over Rod Laver in the 1970 Paris Indoors.

Although he never lived up to the potential he had shown in winning the British junior championship in 1963 and reaching the final of the Australian juniors that year, Stilwell continued to play the international circuit through 1975.

He lost a tough four-setter to Arthur Ashe in the fourth round at Wimbledon that year, and three months later decided to give up globetrotting for the more settled life of a teaching pro in the U.S.

A sociable fellow with a delightful, low-key wit, he had married an American - the former Robyn Lee Kesner, whom he met at a tournament in Glen Cove, N.Y., in 1964. They have three children (Tiffany, 9; Alexander, 7; Lara, 3) and moved here from Baltimore last fall, when Skyline opened.

Stilwell played in and won three local tournaments last spring - in Yorktown, Joppa and Baltimore - and the Castillo event is his first competition since then.

"I'm not really in playing condition, but I'm in pretty good shape. I'm not overweight," said the 5-foot-8, 170-pounder yesterday. He long had a reputation as a richly talented shotmaker who might have had more impact on the pro tour if he had enjoyed training as much as beer, but 35 hours of teaching per week at Skyline apparently has kept him in good trim.

"When I get on the court, I find the competition fun and try to win. But I don't have any desire to play tournaments on a regular basis," Stilwell added.

Not so Sonbol. Despite his busy schedule of work and studies (he has a law degree from the University of Alexandria and is working toward a master's in business administration at the University of the District of Columbia), he adheres strictly to a daily regimen to stay in shape for tournaments.

"I keep practicing just the way I did when I was playing Davis Cup - running, lifting some light weights, playing two hours every day," he said.

"I play very much tennis, but it doesn't interfere with my work except occasionally when I have a match in the middle of the day," he added hastily. "The head of my office is very understanding in these things, and I practice either very early in the morning or very late at night."

Thin and angular at 5-11 and 148 pounds, Sonbol is known as a player who can run and hit balls back all day - a tenacious clay-court player whose passing shots and metronomic steadiness make up for deficiencies in serve and volley. "This is the game of the clay courts on which I was raised - not even Har-Tru," he said, pointing to the artificial clay surface under the huge inflated bubble that covers four courts at Indian Spring, "but slow, red clay."

He credits his wife, Amira Elazhari, with helping him keep in magnificient condition. "She is trying to take care of me, like in old China," he said. "I always took her with me when I was traveling to tournaments, and so she knows about physical conditioning, nutrition and training. We live accordingly. I don't feel any less strong than I did 15 or 20 years ago."

Mrs. Sonbol, a doctoral candidate in Middle Eastern history at Georgetown University, obviously understands the tennis scene. She recently passed her comprehensive examinations and concluded cheerfully, "I think it's like winning Wimbledon."