A bacterial strain (Serratia sp.) that could transform chlorpyrifos to 3,5,6-trichloro-2-pyridinol (TCP) and a TCP-mineralizing fungal strain (Trichosporon sp.) were isolated from activated sludge by enrichment culture technique. The fungus could also degrade 50 mg chlorpyrifos 1(-1) within 7 days. Co-cultures completely mineralized 50 mg chlorpyrifos 1(-1) within 18 h at 30 degrees C and pH 8 using a total inocula of 0.15 g biomass 1(-1).