Since September 11, people want vacations but don't necessarily wish to fly, Fuller said. Many of the timeshares are based within two to three hours of major urban areas.

Timeshare providers say their growth is being fueled by a need for busy families to lock in time together. They also may be less of a hassle than a second home or rental.

John Barrows, an RCI spokesman, says timeshares present a way for hotel companies to diversify. "Most (timeshares) are pre-sold," he adds. "From a business perspective, imagine if Detroit could sell their cars before they had to make them."

Today, there are 1,562 timeshare properties in America and some three million timeshare owners, Tostevin says.

The average timeshare sale is about $13,000, and 67% of timeshares are financed, according to Barrows. The majority of timeshare purchases, 64%, are two-bedroom units. The average annual maintenance cost for timeshares is $414.

The industry went through a major change during the 1990s, when there were a number of independent timeshare companies. "They went public and raised significant capital," Fuller says.

Many of those since have merged. Now the timeshare industry, he says, is consolidated largely in the hands of Cendant, Starwood Hotels & Resorts Worldwide Inc., Marriott International Inc. and Hilton Hotels Corp.

Today, he says, timeshare marketing is much more savvy and cost-effective. Marriott, which owns four brands of vacation ownership-including the Ritz-Carlton Club-is said to have started revolutionizing the business in 1984.

"We don't have that 'you must buy it now' attitude,'" said Marriott spokeswoman Beth Vairo. "Our philosophy, regardless of brand, is we want you to have an incredible experience going through the sales process. We want you to feel better about Marriott walking away.''

Horizons and Marriott vacation clubs, she says, typically offer discounted rates at their timeshare units for three or four nights. In Orlando, Fla., for example, theme park tickets might be included. Although this creates a very economical vacation, those who accept must take a 90-minute tour. Afterward, however, prospects easily can walk away. That is a far cry from timeshare presentations of the past, which had the reputation of all but strong-arming clients into a purchase.