Acid violet 7, a sulfonated azo dye was degraded by Pseudomonas putida mt-2 in mineral medium at concentrations up to 200 mg/L. The genotoxicity of AV7 and its biodegradation extracts was evaluated by using the DNA-strand scission assay. No genotoxicity was observed, even with or without exposition to UV irradiation, for biodegradation under shaking conditions, but increased significantly after biodegradation under static conditions. In addition, the ability of tested compounds to reduce human plasma butyrylcholinesterase (BuChE) activity was evaluated in vitro. Genotoxicity and anti-BuChE activity generated by the azoreduction products [4'-aminoacetanilid (4'-AA) and 5-acetamido-2-amino-1-hydroxy-3,6-naphtalene disulfonic acid (5-ANDS)] were assessed and compared with that of the parent unsubstituted amines. 4'-AA exhibited a strong genotoxicity, which was imputed to the presence of the acetoxy (COCH3) substituent on the aromatic amine; however, the presence of sulphonic groups in 5-ANDS seems to be responsible for its BuChE inhibition activity. The present study demonstrates that P. putida mt-2, incubated under aerobic conditions, has a catabolism that enables it to degrade AV7 and, especially, to detoxify the dye mixtures.