Defending champion Bode Miller of the United States managed only a sixth-place finish in an event that produced a very surprising winner.
Plagued by back problems throughout his career, the 28-year-old Viletta ranks only 49th in the overall World Cup standings this season and he has not competed in any of the slalom races.
His best finish has been a fourth in a combined held in his native country.
Viletta began his day with a time of 1:54.88 in his downhill run, which not only left him in 14th place but also put him a hefty 1.64 seconds behind leader Kietil Jansrud of Norway.
Viletta then turned in a slalom run of 50.32 and it was clear when he crossed the finish line he would move up the final standings. Winning a medal, however, was still unlikely.
As the skiers who had finished in front of him in the downhill took to the slalom course, however, Viletta's time began to look better and better.
Three of those who had been in front of him going into the slalom were unable to finish the course.
Matthias Mayer of Austria, downhill gold medalist and the third-place finisher in the combined downhill, had only the 20th fastest slalom run and wound up in 13th place. Ondrej Bank of the Czech Republic, second quickest in the downhill, was more than three seconds slower than Viletta in the slalom.
And when Jansrud could turn in a mere 53.02 I the slalom, Viletta not only had a medal but it was a gold one.
Viletta's combined time of 2:45.20 was a half second quicker than silver medalist Ivica Kostelic of Croatia. Christof Innerhofer of Italy took the bronze.
Miller, who won the event in Vancouver, was only 12th fastest in the downhill and he improved to sixth overall. He continued a disappointing Olympics, one in which he wound up eighth in the downhill race last Sunday after twice turning in the best training run during the days leading up to the event.