Aerobic bacteria degrading o-nitrobenzaldehyde (ONBA) were isolated from activated sludges. One of the isolates, ONBA-17, was identified as Pseudomonas sp. The isolate could grow on ONBA as its sole source of carbon and nitrogen. Further studies demonstrated that the strain was a moderately halophilic bacterium and capable of degrading benzoic acid, 2-nitrophenol, 2-aminophenol, 4-hydroxybenzoic acid, and 4-dimetylaminobenzaldehyde. It could completely degrade 100 mg L-1 ONBA at a range of pH 6-8 in 48 h at 30 degrees C, and up to 400 mg L-1 after 288 h. The strain showed potential to be a good candidate for biotreatment of industrial wastewaters containing ONBA due to its salt-tolerance ability, multiresistance to some heavy metals and antibiotics, and the abilities of degradation of aromatic compounds. These findings may help in developing a process for ONBA-containing industrial wastewater treatment.