When Diane Dotson is sick, she waits for the wagon.

If she's lucky, it'll only be a few days. But it could be a several weeks before St. Mary's Health Wagon, a free mobile clinic that makes rounds in central Appalachia, arrives in this remote community in southwest Virginia to help the sick.

The clinic squeezes in next to a car wash, parked in Sister Pauline Champagne's front yard, where she chats with patients sitting on lawn chairs in the makeshift outdoor "waiting room." As Sister Champagne calls off each name from her clipboard, patients step into the cramped quarters of a modified RV.

Inside, there are two tiny patient rooms and a bench behind the driver's seat for the next person in line.

Mobile clinics are the main source of health care for thousands living in the mountains, where doctors and health insurance are lacking. Some mobile clinics show up weekly or monthly, others only once a year.

On this particular September morning, Dotson drove 15 miles from her home in Phelps, Ky., to get her blood pressure and heart checked. Dotson, the wife of a disabled coal miner, suffers from high blood pressure and depression.

The couple is buried under a $13,000 debt stemming from an outpatient surgery Dotson had in 1998. Getting health care beyond the mobile clinic is no longer an option.

"I don't know if I'll even live to pay it off," Dotson said. "I don't know what I'd do without the clinic."

Dotson's story is not uncommon in central Appalachia, a region burdened by health care disparities.

Overall, the region has high rates of deaths from cancer, heart disease, diabetes and stroke. Economically, the region lags behind the rest of the nation with high levels of unemployment, low incomes and deficits in education. The region also struggles with the prevalence of illnesses from obesity, smoking and a lack of physical activity.

The rugged, picturesque mountains that keep so many tied to the region only compound the health care problem, keeping doctors scarce and making mobile clinics an alternative to traditional medicine.

"We're their health source," said Ron Brewer, who coordinates the Remote Area Medical Volunteer Corps mobile clinic program for rural Tennessee. "They depend on us as their visit to the doctor."

The services offered by the mobile clinics, typically funded through grants and donations, vary from clinic to clinic.

Some only offer dental or eye care. Others, including St. Mary's Health Wagon, offer virtually the same care offered by a family physician. Most partner with a local physician who reviews serious cases and negotiates referrals with physicians willing to work on such cases.

"We like those days when we can have a sinus infection or an earache," said Netza Mullins, a health coordinator with the Kentucky River Foothills Development Council, which runs a mobile clinic that travels between eastern Kentucky's Powell and Estill counties.

"But because of the lack of health care and lack of health insurance, these folks are very chronic," she said. "Train wrecks is exactly what we call them."

There's no official count on mobile clinics, or the number of people who rely on them. But figures from the annual health fair at Wise, Va. - which draws people from Tennessee, Kentucky and West Virginia - are compelling.

The last event at the fairgrounds, organized by the Remote Area Medical Volunteer Corps, reported 1,377 volunteer health-care professionals who screened and treated more than 8,400 patients from Kentucky, Virginia and West Virginia, delivering nearly $1.4 million in free care over a single weekend in July.

"There's a lot of folks at or below the poverty line," said Stan Brock, head of the RAM Volunteer Corps. "If you look at the profile of people waiting in line, they are clearly in need of help."