The elderly man outside the van who complained of a stomach itch was neatly dressed in a suit, a pen tucked in the inside jacket pocket. Up close, however, the suit was dirty, and the plastic sleeve hanging from a chain around his neck contained not an employee swipe card but a document proclaiming him president and owner of the world government.

Physician's assistant Jack Wintermyer welcomed him inside to take care of the itch without pausing a moment to comment on the document. Wintermyer knew the man well, as he knows many of the homeless and uninsured who come to Unity Health Care's truck for free medical care.

Five days every week, the truck travels to city shelters, parks and social service agencies offering health services to the homeless. Founded in 1985, nonprofit Unity Health Care operates 11 community clinics, nine clinics at homeless shelters, four specialized centers and two vans, making it the fourth-largest community health network nationally. All of its care is free or on a sliding scale, according to chief operating officer Jose Aponte.

The van's first stop, before 8 a.m., was the breakfast program at Miriam's Kitchen at 24th and G streets NW, where social worker Walter Green popped inside to inquire about a few people he had not seen on the streets recently. It took him a while to extricate himself, as it does almost anywhere that homeless people cluster in the District: There is always someone stopping to greet him, tell him how they are or ask for assistance. He left to get medication for one person and promised to take care of another's health insurance recertification.

In the van, Wintermyer and medical assistant Margaret Jones worked their way through the waiting patients: a gaunt man in need of an elbow X-ray, a neatly dressed immigrant from Sierra Leone with heart problems, a man with hay fever who was outfitted like a jogger. Wintermyer wrote a referral for the elbow X-ray. He scheduled an appointment with a cardiologist for the Sierra Leonean, mentally scrolling through the long list of specialists and health centers where he can send patients for treatment not available on the van. He found allergy medication for the hay fever in the truck's supplies.

"I don't know what the homeless would do without this clinic," said the man with the allergies. "I've been coming here for about eight years."

The Sierra Leonean said he was concerned because he had no health insurance. Wintermyer told him what he told all patients with that concern: "We're not worried about the insurance." He did, however, explain how to file for the District's Alliance health care for low-income residents.

The van moved on to Dupont Circle, where the health care workers walked around methodically checking on the bleary-eyed people crashed on benches and blankets, their possessions contained in a couple of bags beside them. Green tapped people on the shoulder, asked how they were doing and apologized for waking them. "Thanks, man," or "Yeah, I feel okay," people told him.

A man whom Green had counseled through a rough period after his brother's death walked up to talk to Green and asked for a couple of bus tokens to go to a doctor's appointment. Before coming to the van, the man had paid little attention to his health, but now he regularly gets his blood pressure checked. "It's a good, good place," he said of the van.

After about a half-hour, the van headed to Georgetown Ministry Center on Wisconsin Avenue NW. On the way, Wintermyer and Green discussed the ways in which poverty, homelessness and disease feed on each other.

"It's not that hard to become homeless, but once you do, it's really hard to get out of it because things are so tenuous," Green said. A person might lose a job because of illness, be evicted for failing to pay rent and suddenly become homeless, in addition to being sick. Someone in that situation who ends up in a hospital emergency room often cannot get prescriptions or follow-up appointments without insurance.

John Craig, manager of Unity's homeless outreach program, said in an interview that health care also tends to become a Catch-22 because of the prevalence of underlying psychological issues among the homeless. "We can't deal with the medical problems without dealing with the psychological problems, and we can't deal with the psychological problems until we've dealt with the grave medical problems," he said. Unity's approach of pairing medical professionals with social workers who follow up and build trust with homeless people is an attempt to solve this dilemma, Craig said.

At Georgetown Ministry Center, the men waiting in the van responded to medical assistant Jones as if she were their mother.

"C'mon, dear," she said to a hulking, middle-aged man wearing pajamas, chiding him for skipping a scheduled appointment.

He hung his head.

She took his blood pressure, temperature and pulse and pricked his finger to test his glucose. "What's wrong with you? Nothing. You just wanted me to take your vital signs, didn't you?"

He grinned sheepishly and decided to fish for attention elsewhere. "Where's the bearded doctor guy, the one who ain't got any hair?" he asked.

Wintermyer stuck his head out of the other examining room. "What are you saying?" he asked.

The man went back to the waiting area.

After Georgetown Ministries, the health workers headed to Franklin Park, then on to Lafayette Square, where they picked up people to take showers at Christ House, where more people were expected for an afternoon clinic.

Unity Health Care medical assistant Margaret Jones, left, and physician Paula Hayes check to see whether any more patients need to be seen before closing the doors of the mobile medical clinic. Unity Health Care van driver Everett Delph, left, sits with Bruce Smith, Dennis Doleman and William Alexander as they await treatment outside a men's shelter on New York Avenue. Unity's mobile unit travels to city shelters, parks and social service agencies throughout the District to provide health and social services to uninsured and homeless people. Its care is free or on a sliding scale.