Maribel Pena, a Harrah's dispatcher aboard its East Chicago casino, sat in a small room furnished with metal desks and boxes of Mardi Gras beads. From this control booth, she electronically monitored every slot machine upstairs.

If a gambler uses a ''Total Rewards'' frequent-gambler card, the slot machine begins to record his every move. The job can keep as many as four dispatchers busy. 

In one effort rolled out first in East Chicago this fall, Harrah's has been dispatching ''luck ambassadors'' to give nominal gifts to big losers -- people who are losing more than expected as tracked by the boat's central computer system and Harrah's loyalty cards. Harrah's has learned that gamblers are more likely to play longer and make a return trip if they receive a small goody.

Richard Pearlman recently lost about $100 at video poker. As he was licking his wounds, Brenda Freeman Winfield, a Harrah's luck ambassador, sidled up to his Deuces Wild machine. Pearlman told her he was feeling ''terrible.''

Tracks players, but not incomes

''This will change your luck,'' she said, handing him a $5 cash voucher. Pearlman, an 81-year-old resident of Buffalo Grove, brightened immediately. A successful intervention, says David Norton, a Harrah's senior vice president of marketing, will leave a customer saying: ''OK, so I lost my $75, but I got two-for-one'' tickets to a Harrah's show.

Harrah's is a leader in using computer technology to boost gambling. The company can trace 75.6 percent of its gambling revenue back to specific customers.

''The player tracking they do is just more effective than what's done by any other competitors in the casino industry,'' says Mark Greenberg, portfolio manager of the AIM Leisure Fund in Denver, who invests in a variety of hotel and gambling stocks, including Harrah's.

But Harrah's walks a fine line. It says it doesn't know its customers' incomes -- a deliberate choice. The company fears being accused of preying on people who can't afford to gamble.

Every morning, casino host Mark Salvador runs through a computer-generated list of gamblers from around the country, looking for people who might be willing to bet more at the Harrah's casino in East Chicago.

On a recent list was a 34-year-old man who hadn't been to a Harrah's Entertainment Inc. casino since November 2003. Before then, according to the data, he had made trips to the Rio in Las Vegas, as well as casinos in Tunica, Miss., and East Chicago. ''This is a customer who can only play when his wife is on vacation or when he's on a trip,'' says Salvador, who planned to call the man and invite him to upcoming events at several Harrah's casinos.

Telemarketing for VIPs

In his gray-walled cubicle in East Chicago, Salvador's job is more of a telemarketer than a traditional casino VIP host. Instead of spending time on the golf course or the casino floor, as hosts do elsewhere, Harrah's hosts must phone at least 240 customers each month. Closely tracked call lists divide gambling prospects into behavior groups: such as ''upsides,'' who have the potential to double their gambling with Harrah's; ''past dues,'' who haven't visited a Harrah's casino in a while; and ''new to me'' gamblers who will get a cold call.

Telemarketing is fueling Harrah's VIP business, which is growing by about 20 percent a year, the company says. Next year, Harrah's plans to give its hosts hand-held computers to log every interaction they have with a customer, even a chat on the casino floor.