A bench-scale air biofilter was evaluated for the removal of volatile organic compounds (VOCs) from a gas stream. Compost and peat were used as the biological attachment media. Biofilter operating parameters such as incoming VOCs concentrations, temperature, and packing materials were examined. After 26 days of acclimation periods, at 25$^{circ}C$ and 45$^{circ}C$, the biofilter removed more than 90% of 30 to 72 mg/㎥ of total VOC. After 40 days of operation, the concentrations of isoprene, toluene, and m-xylene were reduced to 96∼99, 91∼93, and 91∼93% of the original concentrations. VOC removal efficiency was not affected by the temperature. The medium pH was maintained near neutral (pH 6.5∼7.1). After 37 days of operation, the total bacteria count in the biofilter media increased to 1.12${ imes}$10(sup)8 cells/g of medium.