1991: Becomes the first Irish woman to hold a track world record in 5,000 meter indoor event in Boston. Followed by World Student Championship gold in August. That same month O'Sullivan pulls out of World Championships due to burnout.

1992: Expectations soar for the 3,000 at the Barcelona Olympics, but Sonia finishes fourth (behind two Russians and a Canadian), running eight seconds slower than her Irish record, set in Henglo earlier that season. She also failed to reach the 1,500 final.

1993: Following a superb grand prix season, she finished outside the medals at the World Championships in Stuttgart, coming fourth behind three Chinese in 3,000. Comes back strongly to win silver in 1,500.

1994: O'Sullivan takes gold medal in the 3,000 at the European Championships in Helsinki.

1995: World 5,000 gold medal in Gottenburg in August.

1996: The Atlanta Olympics prove one of the lowest pints in her career. She fails to qualify for the 1,500 and did not complete the 5,000 final. Distraught she left Atlanta confused and without an Olympic medal.

1997: Eighth in the 1,500 and seventh in the 5,000 semi-final at the Athens World Championships. Not as bad as Atlanta but not as good either.

1998: In March, O'Sullivan travels to Morocco to win both the long and short races in the World Cross Country championships for an unprecedented double World championship win. A few months later, she wins the inaugural 10,000 event and the 5,000 at the European Championships in Budapest. She beats both the reigning Olympic and World champions.

2000: The Olympic Games in Sydney and O'Sullivan becomes the first Irish woman in history to win a track medal with a silver in the 5,000.