Ingemar Stenmark won his third straight World Cup slalom today, but Austria's downhill ace, Franz Klammer, blocked the Swede's bid for the World Cup lead.

Klammer, who won the Cup downhill race at this Austrian resort Saturday, earned eight points for a fifth-place combined finish today, boosting his World Cup point total to 108.

Stenmark had 104 and is second.

Stenmark won the slalom with a combined time of 1 minute 39.63 seconds. He was tied for the fastest time with Italy's Piero Gros in the first run at 47.66 seconds, but was the fastest in the second with 51.97.

These races were the first this season for which World Cup points were awarded for combined achievements, in addition to points in the individual races. This had been decided by the World Cup committee to encourage all-round skiers.

Italy's Gustavo Thoeni won the combined, by having been 22d in Saturday's downhill and fifth in today's slalom. Stenmark had not entered the downhill. Klammer was far behind in the slalom, but his head start from the downhill netted him fifth place in the combined, which meant eight more points.

Stenmark and Klammer continue their duel next week at Wengen, Switzerland, where points will be awarded in downhill, slalom and combined, just as here.

It was a bad weekend for American skiers. While Karl Anderson of Greene, Maine, finished 19th in the downhill, none of the nine U.S. entries cracked the top 20 in the slalom.

Cary Adgate of Boyne City, Mich., was the best American, in 26th place. Phil Mahre of White Pass, Wash., winner of the season's opening World Cup giant slalom, fell in the second leg. His twin brother, Stevel, also failed to reached the finish.