Despite the widespread use of trickling filters, there has been minimal investigation of the fate of volatile organic contaminants (VOCs) in such systems. A model describing the fate of VOCs in trickling filters is described. The removal of VOCs was investigated in a pilot-scale trickling filter receiving a feed of sewage dosed with a constant concentration of selected VOCs. Increasing hydraulic loading tended to increase the proportion of influent VOCs found in the effluent. Imposing effluent recycle also increased the fraction of VOCs found in the effluent but also decreased the fraction stripped and increased the fraction that was biodegraded. The values of the biodegradation coefficient Kb, were found to be reproducible and affected by a combination of high hydraulic loading rate and effluent recycle.