Mass transfer and bioremediation of toluene from a contaminated air stream has been investigated using a continuous flow, stirred tank bioreactor. The toluene mass transfer coefficients varied from 3.1 to 3.8 h(-1). as the agitation speed increased from 300 to 600 rpm. Using a pure culture, toluene could not be continuously bioremediated as a sole substrate. When ethanol was used as a cosubstrate, toluene was continuously captured and bioremediated at rates up to 90 mg/L(.)h with removal efficiencies up to 90%, while ethanol was simultaneously degraded at rates up to 250 mg/L(.)h. Using benzyl alcohol as the cosubstrate, toluene removal efficiencies were above 97% at continuous loading rates of 90 mg/L(.)h and benzyl alcohol loading rates up to 300 mg/L(.)h.