About 25.5 percent of Texans don't have health insurance, Gallup found. The figure in Nevada is 25 percent and in Alaska 24.9, the polling company said.
Massachusetts has the lowest number of uninsured residents -- 4.1 percent -- followed by Vermont (6.7 percent) and Delaware (8.9), Gallup said.
Overall, 17.2 percent of Americans lacked health insurance in January-June of this year, poll results indicated.
Texas and Massachusetts have been the two extremes in the poll since 2008.
Gallup surveyed 177,670 U.S. adults from January through June 2012. The poll has a margin of error of .3 percentage points.