A study of the fate of volatile organic contaminants (VOCs) in trickling filters (TF) and rotating biological contactors (RBC) was performed. Of the target compounds investigated, tetrachloroethylene was volatilized to the greatest extent, while 1,1,2,2-tetrachloroethane was the least volatilized in the TF and bromoform was least volatilized in the RBC. Toluene, o-xylene and 1,3,5-trimethylbenzene were biodegraded to the greatest extent and 1,1,2,2-tetrachloroethane was least biodegraded. Increasing the hydraulic loading tended to increase the proportion of influent VOCs found in the TF effluent. Imposing effluent recycle on the TF increased the fraction of influent VOCs found in the effluent, but also decreased the fraction stripped and increased the fraction that was biodegraded. Increasing hydraulic loading to the RBC tended to increase the proportion of influent VOCs found in the effluent and off-gas. Increasing the RBC disc rotational speed increased the fraction that was biodegraded and decreased the fraction of VOCs found in the effluent and off-gas streams. The TF tended to have greater losses to volatilization than the RBC while the RBC maintained a greater fraction of the candidate VOCs in the process effluent than the TF. Differences between the processes with respect to biodegradation could not be inferred.