SANTA CLARA, Calif. -- Hollywood has Tom Cruise and Nicole Kidman. Washington has James Carville and Mary Matalin. In New York publishing, there's Tina Brown and Harry Evans. And in Silicon Valley, there's David and Ellen Siminoff.

As Internet expert and money manager for a unit of Capital Group Inc., David Siminoff helps guide the billions of investment dollars fueling the medium's explosive growth, making him -- at 34 years old -- one of the most powerful money men in cyberspace. He is a consummate Big Picture person, funneling capital to a pantheon of online success stories, including America Online Inc. Some Web executives call him "the smoking man," after the mysterious character on television's "X-Files," who pulls the strings behind the scenes.His wife, Ellen Siminoff, is the 31-year-old vice president of business development for Yahoo! Inc. She is the insider, battling on the ground day by day to execute the moves that have made Yahoo the most successful among so-called portal companies vying to be the World Wide Web's gatekeepers. As Yahoo's head deal maker, Ms. Siminoff is regularly approached by everyone from media giants such as Walt Disney Co. to tiny start-ups, all seeking some kind of link with the Internet's most-visited site.

"It's hard to imagine a pair of people in Silicon Valley who are more connected," says Quincy Smith, director of investor relations at Netscape Communications Corp., the Internet software company that is about to be merged into AOL. Mr. Siminoff periodically invests in and advises Netscape, sometimes about ways it might compete with his wife's company. "They rule," Mr. Smith says of the couple.

The male-dominated culture of Silicon Valley hasn't produced many powerful women; even fewer of them are married to powerful men. The Siminoffs are a rarity -- spouses who are equally influential and sought after in their own right. They are the first power couple of the Internet Age.

They don't behave like most other power couples, though. In keeping with the Valley's anti-status culture, the Siminoffs shun publicity and rarely go to parties or charity functions. They like skiing and football and spend most of their free time at home.

If the Siminoffs are far less glamorous than most other industries' power couples, they also are probably much richer. Most of their wealth is in stock investments of various kinds. The Siminoffs decline to discuss their wealth and exactly how much of it there is, but many of Ms. Siminoff's Yahoo peers hold stock and options valued at more than $100 million. Mr. Siminoff has been richly rewarded for his ability to pick hot Internet stocks. He can't trade personally in the stocks he recommends for his employer, but he can invest in Capital Group funds -- a way to "eat your own cooking," he says.

Having each made fortunes astonishingly early in life, the Siminoffs take pride in relatively modest tastes and inconspicuous consumption. Mr. Siminoff has a nice set of golf clubs. Both drive the least-expensive models of luxury cars -- a Lexus for her, a Mercedes for him. They recently moved out of a "bungalow" in Menlo Park and into a French Normandy-style home in Los Altos, where they are closer to his parents' home. "It's decent finally, but not incredible," Mr. Siminoff says.

There are no second and third homes, no opulent vacations -- the couple honeymooned at nearby Pebble Beach so they could golf -- and definitely no private planes. "It's indefensible, and the economics are bad no matter how rich you are," says Mr. Siminoff, who does admit to having upgraded to business class for his commercial flights.

Flaunting their wealth and power, they say, would represent poor judgment and poor taste. "We tend to work a lot and spend the rest of our time with friends and family," says Mr. Siminoff, whose curly mop of brown hair makes him seem like he just emerged from class at his nearby alma mater, Stanford University.

"This isn't a culture where people expect you to dress amazingly well," says Ms. Siminoff, a small, dark-haired women who favors khakis and T-shirts and is a rabid Green Bay Packers fan. She cringes at the term "power couple," and, in the flat accent of her native Milwaukee, says, "Quite frankly, we're dull."

Perhaps, but many people in the online world are fascinated. "You have to wonder what their discussions over the dinner table at home are like, since they touch on everything," says Mary Meeker, a Morgan Stanley Dean Witter Internet analyst.

Ms. Siminoff says at home, she and her husband invariably talk shop. She will often tell him if she thinks certain deals are thick-headed (she gets offered a lot of them first). He will give her Wall Street's reaction to strategic moves in the industry.

Both are firm that they never breach professional confidences or trade information improperly. "If we look as if we are colluding on deals, it wouldn't help either of us," Ms. Siminoff says. Actually, they face fewer conflicts than people might imagine, she says, because Yahoo focuses on small private companies as investments, while Capital Group looks primarily at public ones.

Even Yahoo's competitors say they are certain each Siminoff can keep secrets from the other. George Bell, chief executive of Excite Inc., and Richard Hanlon, AOL's head of investor relations, say they often discuss strategy with Mr. Siminoff. "I think the Siminoffs are proponents of the Chinese wall," says Mr. Hanlon. "And that's a good thing."

Despite their laid-back demeanors, both of them are driven. In high school, Mr. Siminoff was a nationally ranked swimmer, with Olympic aspirations dashed by an injury. He graduated from Stanford and went on to film school at University of Southern California in Los Angeles and worked briefly on Wall Street. Ms. Siminoff graduated from Princeton University, Princeton, N.J., and put in a brief stint at a New York management-consulting firm.

They met at Stanford Business School in 1991 and fell in love while making a killing. Just before starting business school, Mr. Siminoff had traveled in Warsaw and noticed that television in the new consumer economy was awful. In business school he collaborated with his future wife on a venture to trade TV programs for ad time in Eastern Europe. The next summer, the couple went to the region to license "The Care Bears" cartoons, the movie "Mayflower Madam" and other fare to local stations in return for air time. Then they sold the air time at a nice mark-up to American marketers such as Coca-Cola Co. through advertising clearinghouses. Soon, they had made several million dollars from the venture.

Mr. Siminoff found his way to Capital Group, with a recommendation to the company's legendary money manager, Gordon Crawford, from an admiring Stanford professor. Mr. Siminoff considers Mr. Crawford his mentor. Ms. Siminoff took a job working in the online classified division of the Los Angeles Times.

Mr. Siminoff had long been interested in computers and the emerging Internet. Capital Group hired him in 1994 to analyze and invest in the Internet and other media. He soon was evaluating a prospective investment in a small company founded by two young Stanford students, Jerry Yang and David Filo.

Mr. Siminoff met the duo and consulted informally with his wife. Soon the Siminoffs were socializing with Messrs. Yang and Filo. Capital Group would eventually invest $1 million in their obscure Internet-directory company, Yahoo. Ms. Siminoff would provide the entrepreneurs with a free, lengthy analysis of its opportunities, based on her view that the key to Internet success wasn't technology, but rather creating a customer experience. Yahoo, she wrote, should be an "intimate experience and connection" to the content, rather than the delivery method. Creating the content, she noted, was a task better left to others.

"She understood the same thing we had been thinking," says Mr. Yang, "that we shouldn't be thinking like a technology company." The Siminoffs' home is close to that of Mr. Yang and his wife, Akiko Yamizaki, and the two couples often dine together. The Siminoffs have become interested in Ms. Yamizaki's project to wire public schools to the Internet.

Yahoo was a home run for the Siminoffs. The company hired Ms. Siminoff in 1995 to help plot its expansion of its directory with local city versions across the country. Capital Group's initial $1 million stake in Yahoo is today valued at roughly $200 million, although it has sold and bought Yahoo stock over time. Messrs. Yang and Filo are young billionaires.

Mr. Siminoff, meanwhile, was deep into another gamble, on America Online. Immediately after joining Capital Group, he had done well by trading in the volatile stock. Yet by 1996, analysts were writing it off because marketing costs were wiping out its profits. Mr. Siminoff thought it was time to make a far bigger bet. "They were the only company in the online space that was really connecting with consumers, so I thought they were a screaming buy," he says. "But Wall Street sentiment about them was scary."

Mr. Crawford says he made sure Mr. Siminoff understood the stock and then told him to invest his funds as he saw fit. So Mr. Siminoff told his brokers to "suck up every share you can." He also recommended the stock to other Capital Group fund managers. At one point, he recalls, Capital Group had more than $500 million invested in AOL, or 8 percent of the company. It proved to be a stunning coup, as AOL's market capitalization jumped from $3 billion in August 1996 to $45 billion, yielding gains of several billion dollars for Capital Group.

Mr. Siminoff has gone on to make large investments in nearly every major Internet player, from Netscape to Inc. Not every one of them has worked out: He sold a stake in the Internet service provider Netcom Inc. at a loss.

For all their riches, however, Mr. Siminoff hints the couple may end up giving it all away. "We're certainly not going to die with a billion dollars," he says.