Australian Darren Cahill won his second singles title in seven years as a professional by defeating Brad Gilbert, 6-2, 3-6, 6-4, in the championship match of the Volvo-San Francisco tournament yesterday.

The match turned after Gilbert, ranked No. 10, became upset with a line call in the third set. Serving at 30-30, 4-5, Gilbert delivered a first serve that was called wide.

Gilbert screamed: "No. No. God, that was inside the line," then whacked the net with his racket in disgust when it was ruled the call would stand.

Cahill, 25, the No. 6 seed, then set up match point with a cross-court forehand winner, and took the match with one of his best stands of the match at the net.

Cahill, who defeated John McEnroe in the third round and his Davis Cup teammate Wally Masur to reach the finals, earned $32,400 for his victory in the indoor tournament played at the San Francisco Civic Auditorium.

Cahill, ranked 48th, won his only other singles title in 1988 on clay in Gstaad, Switzerland.

Gilbert, seeded third, disappointed the local crowd, who came to cheer for the Piedmont, Calif., native as they did when he defeated top-seeded Andre Agassi in the semifinals, Nonetheless, Gilbert took home $19,090 as the tournament's runner-up. He won this tournament in 1989.

Cahill started quickly, taking the first set in 29 minutes. He broke Gilbert's serve in the first game and went ahead 5-2 by breaking Gilbert again in the seventh game.

Gilbert recovered in the second set, breaking Cahill in the second game to take a 2-0 lead. He then held on, winning game five after surviving three break points. In the ninth game of the set, Gilbert went ahead 40-15 and then needed five set points before evening the match at one set apiece.

Milan Indoor: Alexander Volkov of the Soviet Union won his first Grand Prix title by beating Cristiano Caratti of Italy, 6-1, 7-5, in the ATP tournament.

Volkov, 23, won $77,760 in the tournament in which he was seeded eighth. He plays top-seeded Boris Becker in the first round of the Belgian Open, which begins today in Brussels.

But Volkov said the political turmoil in his country is of more concern to him than that tournament, although he doesn't plan to return home for several months.

Oslo Open: Third-seeded Catarina Lindqvist of Sweden beat Raffaella Reggi of Italy, 6-3, 6-0, to win the tournament in Norway.