Changes
The structure of both the WTA and ATP tours has been changed for 2009. On the men's side, Masters Series events have been replaced by Masters 1000 tournaments, while the International Series Gold and International Series tournaments are now 500 Series and 250 Series events respectively. The season-ending ATP World Tour Finals remains unchanged.
On the women's tour, the tiered system which has existed since 1988 has been scrapped in favour of a structure closer to the men's circuit. Tier I and Tier II have been merged form WTA Premier Tournaments. The Tier III and Tier IV have also been merged into International Tournaments. The WTA Tour Championships remains in the schedule but the WTA have also initiated a second season-ending tournament, the Commonwealth Bank Tour of Champions for eight players who did not qualify for the Tour Championships (usually below the top eight in the rankings).
Read more about this topic: 2009 In Tennis