A flow injection cell-based biosensor was constructed for 2,4-dichlorophenol (DCP) analysis by using a Clark-type oxygen electrode as a transducer. A mixed bacterial culture capable to biodegrade DCP was immobilized between a Teflon membrane and a dialysis membrane and attached to the oxygen electrode. Optimization of the flow rate, the injection volume, the carrier buffer concentration, and pH was carried out. Under optimum conditions (100 mM phosphate buffer, pH 7.50; flow rate 0.10 mL min(-1); sample volume 100 mL), the sensor response was linear between 0.01 and 0.30 mM DCP. The detection limit was 0.02 mM DCP, and the sensor was quite stable during 5 days of operation.