A pilot/full-scale biotrickling filter reactor experiment was performed at an industrial site to treat styrene laden waste gas. The engineered system consisted of two stainless steel tanks in series, each with filter bed volumes of 4.0 m3, filled with 3.5-inch plastic spheres. The system treated 340 m3 h-1 of air laden with styrene concentrations ranging up to 0.8 g m-3. Over the five-month study, styrene elimination was demonstrated up to 24 g m-3 h-1 (35 g m-3 h-1 across the first tank in series) with 70 to 85% removal. Operational and performance problems were identified that differ from those developed under controlled, laboratory set-ups. Operational problems typically involved equipment malfunctions, with the most prone to failure pieces of equipment being the air sampling system and water level sensors. Performance problems were identified that possibly limited the styrene removal. The transient operation of the plant, producing discontinuous, unsteady-state concentrations, made it difficult to establish a stable biofilm on the packing material. Experiments were performed indicating both biological and mass transfer limitations may have occurred.