The German, beaten in the quarter-finals of last week's Italian Open by Martina Hingis, surpassed the previous mark of 331 weeks set by Czech- born Martina Navratilova of the United States.
"This one should stand for a long time. I don't try for records but this is one of them that will always stand out," Graf, 26, said in a telephone link-up from Berlin, where she is playing this week. Ivan Lendl leads all men's No 1s with 270 weeks spent at the top.
"I never was the kind of person who counted the weeks or years, but to hear the number is really amazing," Graf said.
Graf first took the No 1 spot on 17 August, 1987, ending Navratilova's reign. She remained on top for a record 186 consecutive weeks until 11 Mar-ch, 1991, when Monica Seles took over. Graf's current streak as No 1 stands at 49 weeks.
Brighton's Clare Wood will take the first steps towards regaining her place in the world's top 100 when she competes in the first round proper of the Rover International Championship at the National Tennis Centre in Cardiff today. The 28-year-old, who slipped from 78 in the rankings to 187 after suffering a serious hamstring injury, is determined to begin her climb as soon as possible - and has been helped by being given a wild card into the pounds 70,000 event.
"The event in Cardiff will give me the opportunity to earn some valuable ranking points, and I just hope I am able to take that," the three-times British champion said.
The biggest threat is the top seed Irina Spirlea, who beat Arantxa Sanchez Vicario and Mary Pierce on her way to lifting the Florida Open earlier this year.
LATEST WTA RANKINGS: 1= S Graf (Ger); M Seles (US); 2 A Sanchez Vicario (Sp); 3 C Martinez (Sp); 4 I Majoli (Croa); 5 A Huber (Ger); 6 C Rubin (US); 7 G Sabatini (Arg); 8 K Date (Jap); 9 M Maleeva (Bul); 10 B Schultz- McCarthy (Neth); 11 L Davenport (US); 12 J Novotna (Cz Rep); 13 M Pierce (Fr); 14 M J Fernandez (US); 15 A Coetzer (SA); 16 I Spirlea (Rom); 17 M Hingis (Swit); 18 B Paulus (Aut); 19 J Halard-Decugis (Fr); 20 N Zvereva (Bela).Reuse content