His biggest successes though were at the FIS Nordic World Ski Championships, where he earned a total of 8 medals. This included one gold (15 km: 1989), three silvers (4 x 10 km: 1989, 1995 1997), and four bronzes (15 km: 1982, 30 km: 1985, 4 x 10 km: 1982 (shared with East Germany), 1991). In 1998, he earned the Holmenkollen medal (shared with Fred Børre Lundberg, Larissa Lazutina, and Alexey Prokurorov).
During the 2001 FIS Nordic World Ski Championships in Lahti, he tested positive for use of the banned plasma expander Hemohes together with five fellow Finnish cross-country skiers.
This resulted in the disqualification of the gold-medal winning Finnish relay team Following the scandal, Kirvesniemi retired from competitive skiing.
In 2013, he received a 6-month suspended sentence after the Helsinki District Court found that he had committed perjury when witnessing to the court in 2011 that he was unaware of any doping use in the 1990s. Presently Kirvesniemi works as the Plant Manager and Board Member at Yoko Ski.