Toluene, a kind of volatile organic compound (VOC), is widely used as a solvent (paints and coatings, gums, resins, rubber) as well as a reagent (medicines, dyes, perfumes) and is one of the components of gasoline. Over the more recent decades, many studies have led to the development of biological methods to treat toluene. This paper presents the results of a study on the treatment of airborne toluene using a laboratory-scale gas-liquid-solid three-phase airlift loop bioreactor containing immobilized cells. Based on the optimum operating conditions such as the temperature of 28-30 degrees C, pH of 7.0-7.2, and an empty bed residence time (EBRT) of 39.6s, a continuous bioprocess showed that this immobilized airlift loop bioreactor had a steady-state performance within 15days, the outlet concentrations of toluene were lower than the national emission standard in China (GB 16297-1996), and the chemical oxygen demand and NH4+-N of the effluent also satisfied the primary discharge standard in China (GB 8978-1996). In addition, this immobilized airlift loop bioreactor had a good ability to tolerate shock loads, while the maximum elimination capacity of toluene was 168 g m(-3) h(-1) which was higher than those not only in biofilters and biotrickling filters but also in the airlift bioreactor with free microorganisms. (c) 2005 Society of Chemical Industry.