Kristiansen started her career quite unremarkably, running 2:30 to 2:40 for her first few marathons. She won the bronze medal in the 3000 metres at the 1980 World Championships in Athletics and won the 1983 Houston Marathon in 2:33:27 while two months pregnant -- a fact she didn't know until two months later. It was not until she gave birth to her first son, Gaute, that her times began to improve. After winning the Houston Marathon again and the London Marathon in 1984, she placed fourth in the first Olympic women's marathon in Los Angeles. She also set two track world records in the 5,000 m (14:58.9) on 28 June 1984 and the 10,000 m (30:59.14) on 27 July 1985, at the Bislett Games in Oslo.