A dense-phase latex rubber tube and a polyporous propylene hollow-fiber membrane module (HFMM) were investigated for control of benzene-contaminated gas streams. The abiotic mass flux observed through the latex tube was 3.9-13 mg/(min.m(2)) for 150 ppm of benzene at various gas and liquid flow rates, while a 100-fold lower mass flux was observed in the HFMM. After seeding with an aromatic-degrading culture enriched from activated sludge, the observed removal was 80% of 150 ppm, corresponding to a mass flux of 45 mg/ (min.m(2)). The observed mass flux through the HFMM during biofiltration also rose, to 0.4 mg/ (min.m(2)). Because the HFMM had a 50-fold higher surface area than the latex tube, the observed benzene removal was 99.8%. Compared to conventional biofilters, the two reactors had modest elimination capacities, 2.5-18 g/(m(3).h) in the latex tube membrane bioreactor and 4.8-58 g/(m(3).h) in the HFMM. Although the HFMM had a higher elimination capacity, the gas-phase pressure drop was much greater.