I can't stand it when someone tells me I can't have something," says Jan Stephenson. "I have to prove them wrong."

Her father tried first, pleading with her—unsuccessfully—not to give up tennis for golf at age 10. Then a stuffy tournament official warned Jan at 15, when she had become the youngest player ever to win Australia's junior title, that golf was no career for a lady.

Proving them wrong was right for Jan. At 24, she is the hottest young player on the women's pro circuit and a favorite to win the U.S. Open this week in Springfield, Pa.

To hear Jan tell it, a fierce will to win was programmed into her at childhood. "I began swimming competitively when I was 8," she says. "Sports of all kinds have always been very important in my life."

Her father, a transportation worker in Sydney, Australia, moved the family into a beach house 60 miles north of the city so the children could participate more easily in athletics. Her only brother, Greg, 22, a landscape architect, is himself an accomplished golfer. "Tennis was free, the ocean was nearby for swimming, and golf was only 10 cents a round," she says. "In Sydney it would have cost my father a fortune."

After taking up golf, Jan worked at it for two years, then breezily announced at 12 that she wanted to quit. "I told my father that I needed a surfboard so I could train to become a professional surfer," she laughs. "Instead of saying no, he said he would buy me one when I got my golf handicap below 18. Well, I went crazy, practiced constantly and about five months later—on my 13th birthday—my handicap was down to 18. But his little trick had worked. I told him I wanted a set of new clubs instead of a surfboard."

A few months later she won the New South Wales junior title and held it for four straight years. She won the Australian junior title three times from 1967 to 1971. At 19 she was voted her state's outstanding female athlete.

"I wanted to turn pro," she says, "but I knew it cost a lot of money. Before the Australian Open in 1970, Bruce Devlin [who plays on the U.S. men's pro circuit] told me that if I won, he could line up an American sponsor for me. Well, I finished second and I went home feeling very depressed.

"I was determined to get to the States. It occupied all of my thoughts. I had been going out with a guy who was really loaded. He kept telling me he wanted to marry me, and once he had said he would buy me a Mercedes and send me to the States if I would just say yes. So I did. We got married and it was pretty bad. I still hoped he'd send me to America and buy me a Mercedes," she says, "but instead he dragged me off to London on business. I couldn't stand it, so I returned home and divorced him."

For the next two years, while she sharpened her game and settled her personal life, Jan was a sports columnist for the Daily Mirror in Sydney. In August 1973 she finally turned pro, and before the year was over she had entered 10 tournaments in Australia, winning four and never finishing lower than fifth.

In 1974 Jan moved to the U.S. and was an instant success. In her first tournament she finished second and eventually won Rookie of the Year honors. This year she has won two tournaments, was runner-up in the prestigious Women's Masters and tied for third in the rich Colgate-Dinah Shore Winners Circle championship. "I can't see me doing anything else but playing golf for the next 10 years," Jan says. "I take the game very seriously."

She maintains a condominium at the Canyon Country Club, Palm Springs, Calif., which she represents on the tour. She devotes most of her spare time to practice, but does squeeze in some yoga, junk reading and telephoning. "One month I ran up a $1,500 phone bill," she laughs. "My manager blew his stack." She takes most of her meals in her hotel room. "I want to be famous very badly," she confesses. "Women's golf needs a superstar—like Chris Evert or Billie Jean King. I'd sure like it to be me."