The hydrogen and volatile fatty acids production in a anaerobic fluidized bed reactor containing expanded clay like a material to immobilize acclimated anaerobic sludge was evaluated. The reactor was seeded with a heat treated sludge at 90oC for 10 minutes for enriching H2 producing inoculum and supressing methanogens. The system was operated at hydraulic retention time (HRT) of 8.0-1.0 h and was fed syntetic wastewater containing glucose (2.0 g.L-1). At 30 oC and pH 3.8, about 92-98% of glucose was removed. The decrease of HRT from 8.0 to 1.0 led to a marked increase in the mean volumetric H2 production rate from 0.26 to 1.03 L.h-1.L-1, respectively. The maximum volumetric H2 production rate, 1.28 L.h-1.L-1, was obtained at HRT 1.0 h. In general, the H2 yield decrease with HRT from 3.34 mol H2.mol glicose-1 at 8.0 h to 2.16 mol H2.mol glicose-1 at 1.0 h. The biogas was free methane and the H2 content accounted for 37% at HRT 2.0 h. There was a linear correlation between the production rate and the organic loading rate (OLR) and the maximum OLR, 104 Kg.m-3.d-1, is not expected to inhibit hydrogen production. The major soluble products were butyric acid (45.52- 62.91%) and acetic acid (19.69-45.73%) further ethanol was relatively insignificant (less than 7.0%). The stable hydrogen production and the percentagen of butyric acid over acetic acid indicated the heat treated sludge was effective and a typical butyrate type fermentation was achieved by Clostridium.