Wassberg, who started for Åsarna IK , took 15th place over 15 km and fourth place with the relay at the 1976 Winter Olympics in Innsbruck . The following year he finished second in the 50 km at the Lahti Ski Games . and won the unofficial overall world cup. In 1979 he won the Holmenkollen Ski Festival for the first time over 15 km and took third place with the relay at the Svenska Skidspelen in Falun . At the 1980 Winter Olympics in Lake Placid , he won the gold medal over 15 km. He was ahead of the Finn Juha Mieto by a hundredth of a second. After this, the closest of all possible decisions, the time measurement for future cross-country races was changed to tenths of a second. A proposal by Wassberg to share the gold medal found no support from the IOC . He was also fifth with the relay and fourth over 30 km. In the same year he won the Holmenkollen Ski Festival over 50 km and the Svenska Skidspelen with the relay. He then received the Svenska Dagbladet gold medal and the Holmenkollen medal . He turned down the Svenska Dagbladet gold medal to protest against an earlier decision by the award committee. At the Svenska Skidspelen in 1981 he won the 30 km run. He made his debut in the official cross-country skiing world cup in January 1982 in Reit im Winkl and took third place over 15 km. Second places followed in Le Brassus and Štrbské Pleso, each over 15 km. At the highlight of the season, the Nordic World Ski Championships in 1982 in Oslo , he won the gold medal over 50 km. He also achieved 18th place over 15 km, 16th place over 30 km and fifth place with the relay. At the Svenska Skidspelen in 1982 and since the 1981/82 season at the same time World Cup in Falun, he came third over 30 km and second place with the relay. He finished the season in second place in the overall World Cup. In the following season he reached five top ten placements in the World Cup, including third place over 30 km in Labrador City and second place over 30 km in Falun and thus achieved fifth place in the overall World Cup. He also finished second in Falun with the relay. In the 1983/84 season he finished second over 15 km in Lahti and over 30 km in Falun. He also won the relay in Falun. At the 1984 Winter Olympics in Sarajevo , he won the gold medal over 50 km and with the relay. Over 30 km he achieved 14th place. At the end of the season he finished second in the overall World Cup. After eighth place over 15 km in Cogne at the beginning of the 1984/85 season, he won the bronze medal with the relay and the silver medal over 15 km at the Nordic World Ski Championships in 1985 in Seefeld in Tyrol . He was fourth over 30 km. In March 1985 he took third place over 30 km in Falun and second place with the relay and won the 15 km race in Oslo. At the end of the season he came third in the overall World Cup. In his only World Cup start in the 1985/86 season, he won the classic 30 km in Falun. After sixth place in Ramsau am Dachstein and fifth place in Davos at the beginning of the 1986/87 season, at the peak of the season at the Nordic World Ski Championships in 1987 in Oberstdorf he won the silver medal over 15 km classic and over 50 km freestyle and over 30 km classic and with the Relay the gold medal. In March 1987 he won in Falun with the relay and in Oslo over 50 km classic. She finished the season in second place in the overall World Cup. In his last active season 1987/88 he came in the top ten three times in the World Cup and finished 19th in the overall World Cup. At the 1988 Winter Olympics in Calgary , he was again Olympic champion with the relay and also achieved 42nd place over 30 km classic. In Swedish championships he won four times over 15 km (1979, 1980, 1982, 1983), three times over 30 km (1979-1981) and once over 50 km (1980). With the season of Åsarna IK he was champion seven times (1980-1983, 1985, 1987, 1988).