In this study, the performance of a biotrickling filter (BTF) treating complex mixtures of VOCs from pharmaceutical industries was evaluated. Effects of inlet loading rate (ILR) and empty bed residence time (EBRT) on elimination capacity (EC) and removal efficiency (RE) were evaluated. Methanol, ethanol, acetone and toluene were taken as model pollutants. The net inlet concentration was varied from 1 to 4g/m3 to achieve an ILR variation from 52 to 419g/m3/h, while the EBRT was varied from 25 to 69s. The BTF was able to completely degrade the VOCs up to an ILR of 240g/m3/h, while treating mixed pollutants. On the other hand, 100% RE was achieved for ILRs up to 320g/m3/h in case of single pollutants and the corresponding maximum elimination capacity (ECmax) for ethanol and acetone was 380g/m3/h. However, the ECmax was only 320g/m3/h for the BTF treating mixed pollutants. Competitive interactions between different pollutants resulted in significantly lower ECmax for individual pollutants in a mixed pollutant system than those in a single pollutant system. Toluene was the most resistant to degradation, followed by acetone, among the four pollutants studied. It was found that much of the degradation of ethanol and methanol occurred in the first 30cm of BTF. It was also observed that the ILR and nature of the pollutants significantly affected the RE achieved at different EBRTs. Results from this study help in selecting the operational parameters for optimal performance of a BTF treating complex mixtures of VOCs emitted from pharmaceutical industries. © 2012 Elsevier B.V.