Wins Nordic World Cup
In 1982, Koch became the first American to win a medal in a world championship Nordic competition; he finished third in the 30-km race in Oslo, Norway. In the same year, based on that season's results, he won the overall Nordic World Cup title.
In 1983, Koch won the 30-km and 50-km events and came in second in the 15-km race at the U.S. National Championships. He also led the World Cup rankings until the last three races of that season, and placed third overall in the World Cup championship. Koch went to the Olympics, held in Sarajevo, Yugoslavia, in 1984, where he competed in four events. He did not earn any medals at these Games.
In 1986, Koch's fight to introduce a new skiing style was victorious. The World Cup officials decided to allow his skating technique, but hold separate races for skiers who used the new skating stride and those who used the traditional diagonal stride.
Also in 1986, Koch came up with the idea of inventing a single layer of fabric that would be suitable for ski clothing, which traditionally has used multiple layers. Although the right fabric was finally invented in 1992, the same year Koch licensed his line of clothing to a company called Sport Hill, its manufacturing process was subsequently changed, eliminating the fabric's resistance to wind. Because of this, Koch's clothing line was dropped.
Koch retired temporarily in 1987, but came back to competition for the U.S. at the 1992 Olympics in Albertville, France. He did not medal at those Olympics, but he was chosen to carry the U.S. flag during the opening ceremonies. Koch told Bergin, "That was a very great honor to have been chosen by my peers to do that."
Although Koch competed in the 1994 Olympic trials, he did not make the final team.
Koch believes that his international wins can be repeated by other American skiers. In an interview in Ski, he told Andrew Bigford, "I don't think I'm that special. There's plenty of talent out there. What I did is repeatable." He founded the Bill Koch Ski League, a national cross-country ski program for children aged seven to thirteen, to encourage kids to ski and develop their talent. Koch told Bigford that he believed the sport was hampered by the fact that good snow for the sport is not always available, since most people don't live in snowy areas and for those who do, the weather and snow conditions are so variable. "If you could count on snow, I think cross-country would flourish."