She was born in Nyeri district in 1972. It was while attending Ngorano Secondary School that she started to pursue a running career. In 1994 she joined Kenya Prisons. She made her international debut in 1995 in a 10K road race in South Korea. In 1998 and 1999 she was voted road racer of the year by two prominent running magazines after winning 8 races.
In 2000 she won the Boston and Chicago marathons. In 2001 she won the two marathons again. She also set a world marathon record at 2:18:47 in Chicago. That year she was named female athlete of the year by the IAAF.
In 2003 she won gold at the world athletics championships and in 2004 she won silver at the Olympics. She won gold again at
the 2007 World athletics championships and silver again at the 2008 Olympics.Her performance in international competitions is most commendable considering that marathoners rarely represent their nations in competitions such as the Olympics. She has represented Kenya at international competition better than any other marathoner male or female.