Bioremediation of nitrobenzene-polluted sediments was studied through lab-scale and in situ experiments. The polluted sediments were remediated through the addition of bacterial separated from the sediments, even at a low temperature of 5 degrees C. Nitrobenzene at a concentration of 11.8 mg/kg was biodegraded within 4 d with the addition of 2 mL cell solution (10(7) cells/mL). No extra nutrients were needed for the bioremediation process, showing that enough nutrients existed in the sediments. For the in situ bioremediation experiment, the initial nitrobenzene concentrations at solution and sediments were 50-61 mg/L and 7-8 mg/L respectively. The remediation process was also enhanced through cell addition. The above mentioned nitrobenzene was biodegraded within 48 h, compared with 96 h without cells presence. Nitrobenzene in solution was removed preferentially than those in sediments.