Andy Roddick became the new No. 1 in men's tennis Monday, overtaking Juan Carlos Ferrero for the top ranking.

Kim Clijsters remained No. 1 among the women, with Belgian countrywoman Justine Henin-Hardenne at No. 2. Neither played last week.

Roddick, the U.S. Open champion, lost in the semifinals of the Paris Masters but had been assured the top spot when the ATP released its latest rankings. Ferrero lost in the third round in Paris.

Roddick has 4,335 points and Ferrero 4,205. Roddick, 21, is the fourth-youngest player atop the computer rankings since the ATP Tour introduced them in 1973.

Completing the top 10 are Roger Federer, Guillermo Coria, Andre Agassi, Rainer Schuettler, Carlos Moya, David Nalbandian, Mark Philippoussis and Sebastien Grosjean.

The entry system rankings reflect the past 52 weeks and are used to determine tournament seedings. The season-ending Tennis Masters Cup starts this weekend in Houston.

In the WTA rankings, five Americans are among the top 10: No. 3 Serena Williams, No. 4 Lindsay Davenport, No. 5 Jennifer Capriati, No. 7 Venus Williams and No. 10 Chanda Rubin.

The WTA Tour Championships begin in Los Angeles on Wednesday (ESPN2, 10:30 p.m. ET).