Imagine having a personal physician at your disposal within minutes, 24 hours a day.

Out of town on business? Tied up at the office? No problem. Just call that cell-phone number tucked in your wallet. Your doctor will race to your side.

Sound like a fantasy? Not in Seattle. The city that spawned service giants such as Nordstrom and Starbucks, and new retail concepts such as Costco and Amazon. com, has begun a quiet revolution in medical care. A niche market, sometimes called "retainer medicine," has taken root in Seattle with at least three such practices thriving and one poised to expand nationwide.

The idea started five years ago when Dr. Howard Maron, former team doctor for the Seattle SuperSonics, started MD2 (pronounced "MD squared") with his partner, Dr. Scott Hall.

"It's like the Ritz Carlton," said Duane Dobrowits., chief executive officer of MD2. Fine artwork hangs on the walls. The bathrooms are lined in marble. And for the ultimate in privacy, the doctors allow only one patient on the premises at a time.

Two lower-cost versions of the same idea -- Seattle Medical Associatesand the Lewis & John Dare Center at Virginia Mason Medical Center -- also are growing. Both recently added physicians to accommodate patient demand, and even that's not enough. The doctors who run Seattle Medical Associates each have more than 100 people on waiting lists.

It's likely to be a long wait. Turnover is low.