This research work investigates the biodegradation of 2-chlorophenol vapours in a trickling biofilter packed with a ceramic material, and seeded with a pure strain of Pseudomonas pickettii. The process was tested at laboratory scale over 260 days of operation under varying loading conditions. More than 98% degradation efficiencies were achieved for loading rates up to 82.5gm(-3)h(-1). Process analysis, performed using data on 2-chlorophenol concentration profiles along the biofilter bed, shows that best biofilter performance (i.e. maximum degradation capacity and efficiency) can be obtained for a narrow range of operating conditions, which can be ensured by proper sizing of biofilter diameter and height.