Teflubenzuron baits were active against laboratory colonies of the red imported fire ant, Solenopsis invicta Buren. Worker brood production ceased soon after treatment and by four weeks posttreatment, most colonies were devoid of brood. Worker ants did not exhibit any direct effects from treatment with teflubenzuron. As is typical with most insect growth regulators, colony mortality was slow and dependent on old-age attrition of the worker ants. A few (<25) female alates were produced in one of the laboratory colonies at 12 weeks posttreatment. The teflubenzuron baits reduced field colonies of S. invicta by 75-79% within 6 weeks after treatment, 83-86% within 13 weeks, and 77-91% within 17 weeks. At 17 weeks posttreatment, the presence of worker brood in the plots treated with the lower rates, 0.1125% and 0.0225%, gave evidence of recovery of some colonies. However, the results of the field tests indicate that teflubenzuron has excellent potential for control of field populations of S. invicta.