Summary: A bacterium capable of utilizing the selective herbicide 2,2-dichloropropionate (2,2DCP; Dalapon) as sole source of carbon and energy was shown to possess inducible dehalogenase activity. Enzyme activity was also induced by numerous other haloalkanoic acids. Chlorinated compounds were generally better inducers of dehalogenase than the corresponding brominated compounds. Cell extracts of 2,2DCP-grown bacteria liberated free halide ion from several C-2 substituted alkanoic acids; C-3 and C-4 monosubstituted acids and halogenated acetamides were not attacked. Brominated compounds were dehalogenated more readily than the corresponding chlorinated compounds. Gel electrophoresis of cell extracts indicated the presence of at least two dehalogenases in 2,2DCP-grown bacteria. These were separable by ion-exchange chromatography. Both partially purified dehalogenase activities had a fairly broad specificity, attacking several haloalkanoic acids in addition to 2,2DCP. Monohalogenated acetates were substrates for one of the dehalogenase activities but were potent inhibitors of the other. The two activities differed in their susceptibility to thiol-blocking reagents but had similar apparent molecular weights.