An aerated microbiological process was tested in 1.5-1 stirred tank reactors for the treatment of dimethylamine salt of 2,4-dichlorophenoxyacetate (2,4-D). A mixed culture was used with the concentration range of 54 to 216 mg 2,4-D/l. The highest concentration was completely depleted within 6 to 8 days of contact time. 2,4-Dichlorophenol, the first intermediate of the degradative pathway, accumulated transiently in the growth medium.