Marc Girardelli won the men's slalom in Kranjska Gora, Yugoslavia, and clinched the World Cup season title by edging Sweden's Ingemar Stenmark.

Girardelli was ninth after the first run, but was nearly flawless the second time down. His winning time of 1 minute 43.11 seconds was .05 seconds better than the 1:43.16 posted by Stenmark, who led Girardelli by .61 seconds after the opening round.

"We all can have two perfect runs, while Girardelli can allow a slow run or a mistake," said Stenmark.

Jonas Nilsson of Sweden, who won the World Championship slalom, skied to a third-place tie with Paul Frommelt of Liechtenstein. Both were clocked in 1:43.88.

The victory was Girardelli's fifth of the season in slalom.

Stenmark, who indicated he might return for a 13th World Cup season in 1986, took second place behind Girardelli in the slalom standings with 78 points and seventh place in the overall standings with 115 . . .

Eva Twardokens, the most consistent U.S. skier on the World Cup circuit this season, capitalized on a fall by Diann Roffe and won the women's giant slalom at the U.S. Alpine Championships in Copper Mountain, Colo.

Roffe, 17, who won a giant slalom gold medal in the world championships earlier this month, had built a lead of 1.56 seconds over Twardokens after the first run. But she lost control early in her second run and fell.

Team physician Courtney Brown said Roffe suffered a bruised left knee and would not ski in today's slalom, but should be fine for the next World Cup races in Vail, Colo., March 2-3.

Twardokens had a second-run time of 1:09.79 for a combined time of 2:13.04, giving her a narrow victory over Karen Lancaster (2:13.07).

Cindy Nelson finished third in 2:13.56 and Olympic champion Debbie Armstrong (2:13.58) was fourth.

"The wind was blowing hard up there, and the gates were really leaning," said Twardokens, 19, of Squaw Valley, Calif. "You had to duck under the gates sometimes, and that made it hard to concentrate." . . .

Olympic and world champion Gunde Swan of Sweden won a 15-kilometer men's World Cup cross-country ski race in Sofia, Bulgaria. Swan covered the distance in 41 minutes 6.5 seconds, followed by Norway's Thor-Hakon Holte in 41:15.1.