Imported fire ant colonies from 6 sites in Brazos and 1 site in Madison County contained numerous functional queens, while colonies from 1 site in Chambers County and 1 site in Madison County contained only 1 functional queen. Workers from multiple-queen mounds were tolerant of ants from neighboring mounds, but workers from single-queen mounds were not. The multiple-queen trait may be spreading in Texas, and may make the control of fire ants even more difficult.