Twelve Texas counties lead the nation as having the highest percentages of children lacking health insurance — and the state's adult population isn't faring much better, according to a first-ever estimate by the Census Bureau.

Overall, Texas rates second-worst in health coverage among states, behind only New Mexico. Six of the 10 counties with the lowest percentage of health coverage for all age groups are in Texas, largely in its southern and western regions.

Bexar County — where about one in five people go without health insurance — is doing somewhat better, but still rates 231st in uninsured children and 433rd overall out of 3,140 U.S. counties.

Sen. Judith Zaffirini, D-Laredo, said while she believes the state is doing better now — the estimates are based on data from 2000 — there is still an uphill battle to be waged for better health coverage.

"I am surprised; I thought Texas was doing a lot better," she said. "It'll be very helpful for us in the future because decision makers in Texas believe we've made great strides, and we have, but clearly we have a long way to go."

As vice chairwoman of the Senate Finance Committee, Zaffirini helped hammer out the budget for health and human services in the most recent session.

"In 2005 we restored a lot of services," she said.

Hudspeth, a far West Texas county that borders El Paso, is last in the country when it comes to the percentage of uninsured, among both adults and children.

The mostly rural county is also without health care — there are no doctors, except when Planned Parenthood operates a general health clinic every other Saturday, said Abigail Ortega, county administrator.

"It doesn't surprise me that we're in this condition," she said. "These are small communities and every business is a half-hour or an hour away."

While the new census data provides a good broad-brush portrait of parts of the country that are underserved, state demographer Steve Murdock warns it needs to be taken with a grain of salt.

Murdock, who teaches in the University of Texas at San Antonio's business department, said the estimates are volatile and experimental.

"They simply don't have the data to do this," Murdock said. "I would use it with substantial caution and only to look at regional differences, not to look at one county versus another."

The estimates are based on surveys, food stamp and Medicaid participation records, aggregated federal tax return data and demographic population estimates.

Murdock stresses that census officials have to work with data that's out there, and have been ordered by Congress to produce the estimates.

"It's not that they've done a bad job," he said. "The uninsured is a big issue in the United States and what they're doing is a very important thing to do."

Mike Bergman, a spokesman for the Census Bureau, said the estimates will be updated annually.

"This is a start for us," he said. "We've never been below the state level for health insurance estimates."

Dr. Bill Hinchey, a San Antonio pathologist and chairman of the board of trustees of the Texas Medical Association, said the uninsured place undue burden on emergency rooms.

"A lot of these people will get their basic medical care in the emergency room, and that clogs our emergency rooms for truly emergent care," he said, adding that his group is grappling with solutions. "How do you grab Jell-O? It's a complicated issue."