Richard Montefusco of Westwood became the only Washington-area golfer to gain the semifinals of the ninth annual South Atlantic Junior championship at Crofton yesterday.

He was joined by Bob Wrenn and Dick Getek both of Richmond, and Bill McGuiness of Woodbury, N.J. Montefusco plays Wrenn and McGuiness Plays Getek this morning. The final will be played this afternoon.

Montefusco defeated Dan Reardon in the morning and then got past Charles Gates of Columbia, 3 and 2, in the afternoon. Wrenn ousted Keith Leetun in his first match and then disposed of Greg McCullough, 2 and 1, in the afternoon.

McGuiness eliminated Craig Rank in his first match and then beat Mark Kingham, 2 up, in the afternoon. Getek defeated Tony Milam in the morning but had a tougher time against John Colheb, of Westport, Conn., in the afternoon, winning, 1 up.

In one of the best of the morning matches, Collich defeated Dan Bosis of Indian Spring on the 20th hole. Bosis had a chance to win it on the 18th but made a mistake in trying to putt out of a trap. He wound up with a bogey to halve the hole. The first extra hole was halved, then Collich birdied the 20th from 10 feet.

In his afternoon match with Gates, Montefusco was 1 up at the turn and took the 10th and 11th to increase his margin to three holes. Gates won the 12th with a par and the 13th and 14th were halved. Montefusco rammed in a 50-foot birdie putt on the 15th to go 3 up again and the 16th was halved to end the match.

Wrenn was 3 up at the turn and then McCullough steadied down. McCullough held on through the 16th but by then he had run out of holes. McGuiness was 1 up going to the 18th in his match against Kingham and clinched it with a 30-foot birdie putt.

Colich and Getek were all even through 16. Getek was on the green with his tee shot on the short 17th and won it with a par when Collich made a beautiful recovery from a trap but missed a three-foot putt. The 18th was halved in par.