MANHATTAN BEACH, CALIF., AUG. 16 -- About the only person at the $250,000 Virginia Slims of Los Angeles tournament unaware the No. 1 ranking in women's tennis was at stake today was Steffi Graf.

Graf, 18, kept from knowing by her father, completed her rapid ascent to the top spot with a 6-3, 6-4 triumph over Chris Evert. The tournament title was Graf's eighth of the year and 16th of her brief career.

More important, her 50th victory in 51 matches this year elevated her past Martina Navratilova on the Women's International Tennis Association computer. She is the first No. 1 other than Navratilova or Evert since Tracy Austin in July 1980.

Navratilova lost, 6-2, 6-1, to Evert in Saturday's semifinals. Had she beaten Evert, she would have remained No. 1, regardless of today's outcome.

Peter Graf, father-coach of the West German sensation, shielded from her the fact a victory would give her the top ranking.

"I talked about {gaining the top spot} with my father after Martina lost and he said, 'No, it's not possible,' " Steffi Graf said.

"After I won, my father said, 'How does it feel to be No. 1?' I was so surprised."

"I knew," he said, "but did not want to tell her. She's under unbelievable pressure already."