Confrontation behavior of the imported fire ant, Solenopsis saevissima richteri Forel, and Lasius neoniger Emery was studied in the laboratory and field. Workers of L. neoniger attacked those of S. saevissima richteri. Usually an antenna of the imported fire ant was seized and passed between the clypeus and mandibles of L. neoniger. The L. neoniger sprayed a secretion from the acidopore of the gaster into the imported fire ant's facial area; many imported fire ants were killed. Although imported fire ants had difficulty getting close enough to sting, the venom secreted from the sting was fatal to L. neoniger workers. A laboratory confrontation index showed that L. neoniger workers could destroy 2 to 3 imported fire ants for each one of its own killed. Eventually L. neoniger colonies were destroyed by the overwhelming number of workers in the imported fire ant colonies.