Dichloromethane (DCM) is a kind of volatile organic compound (VOC), and many biological technologies have been studied and applied to meet the treatment of the waste gases. In this paper, a new bio-contact oxidation reactor, in which biofilm attached on the assembly semi-soft plastic media filled in column, was set up to removal DCM from waste gases. The influences of empty bed residence time (EBRT), temperature, pH and organic load on the removal efficiency (RE) and the elimination capacity (EC) of DCM were investigated and discussed. The optimum operation conditions were obtained as the temperature of 20-30 degrees C, pH 6.0-7.0 and EBRT of 28.3 s for the inlet gas concentration range of 500-1260 mg/m(3). Under the optimum operation conditions, the average removal efficiency of DCM was higher than 82%, at the inlet concentration of DCM lower than 1260 mg/m(3). The maximum elimination capacity (ECmax) of DCM in the bio-contact reactor was higher than that in the biofilters reported in the literature under the same operation conditions. (c) 2006 Elsevier B.V. All rights reserved.