Niki Lauda, driving a McLaren, increased his lead in the Formula 1 drivers standings by winning the Italian Grand Prix in Monza yesterday.

The crowd of 100,000 waved Italian flags as Michele Alboreto's Ferrari finished second and Riccardo Patrese's Alfa Romeo third.

Lauda bided his time until the 39th lap, when he passed Teo Fabi's Brabham, which was running second. Then, three laps later, he caught Renault driver Patrick Tambay. He won in 1 hour 20 minutes 29.065 seconds, averaging 137.025 mph.

"I had planned to make a move in the final 15 laps," Lauda said. "It wasn't tough to pass them. The car did exactly what it was designed for. It's most important that nothing broke."

It was his fifth Grand Prix victory this season. With two races left, he has 63 points, 10.5 ahead of Alain Prost, who made only four laps yesterday. ("The motor just broke," Prost said during a long walk back to the pits) . . .

At Richmond Fairgrounds Raceway, Darrell Waltrip got new tires for his Chevrolet, then earned $46,550 by pulling away in the 216.8-mile Wrangler 400 NASCAR Grand National. It was his fifth victory this season, best on the Winston Cup circuit. He led the first 200 laps, except when he pitted under caution on laps 153 and 157. But when Waltrip pitted on lap 215, Ricky Rudd closed in and on lap 276 took the lead.

"Up to that point (the pit stop on 215), we could just about run away from everybody at will," Waltrip said. "But we had problems for a hundred or so laps with a set of tires. The left front tire had a little hole in it."

When Trevor Boys spun out on lap 342, Waltrip and Rudd used the opportunity to pit. Rudd got new tires, too, but Waltrip beat Rudd out of the pits and took the lead.

Rudd finished five seconds behind and Dale Earnhardt came in third. Waltrip averaged 74.780 mph and led 313 of the 400 laps . . .

In St. Pie, Quebec, Danny Sullivan of Louisville pulled away from pole-sitter Bobby Rahal at the end to win the Molson Indy 300-kilometer race on the new seven-eighths mile track at Sanair Super Speedway.

Despite a sunny and mild day, fewer than 10,000 saw the first Indy-car race in Canada since 1978 and the first ever in the province.

Lola T-800 cars have won the last seven races on the circuit. Mario Andretti won five of them, and Sullivan has won two of the last three. Sullivan, who led the last 91 of 225 laps, averaged 111.707. Bobby Rahal's March 84C was second. Rahal led until pitting on lap 107. Michael Andretti was third, Josele Garza fourth and Johnny Rutherford fifth. Rutherford was substituting for the injured Rick Mears.

Mario Andretti (seventh yesterday) leads the point standings with 122; Tom Sneva has 111, Mears 110 and Sullivan 108. Four of 16 races remain on the schedule . . .

Mears, who suffered a cerebral contusion and severe foot injuries while practicing for the Molson, was flown to Indianapolis, where both legs were put in casts. If the swelling subsides, he'll have surgery Tuesday. He likely will need several operations, and doctors say he'll need three months to recuperate and another three months for rehabilitation. Before leaving Canada, he was alert, in good humor and chatting with visitors.