During a field evaluation of a boric acid bait against the red imported fire ant, Solenopsis invicta Buren, it was observed that workers of intoxicated colonies produced stings with less toxic effects compared with workers from healthy colonies. The present study was undertaken to investigate the effect of boric acid on the levels of piperidine alkaloids in ant venom was investigated. Exposure to boric acid for a period of 4 wks resulted in significant changes in both concentrations and ratios of the piperidine alkaloids. The concentration of piperidine alkaloids was significantly lower in colonies treated with the boric acid bait. Thus, boric acid suppresses the production of piperidine alkaloids in red imported fire ants.