Suspended and immobilized anaerobic sludge were utilized to produce hydrogen gas in batch reactors using sucrose as the sole carbon substrate. A variety of immobilization matrices and methods were examined for their suitability to make immobilized H-2 producers. The results show that cells immobilized by calcium alginate matrix supplemented with chitosan and titanium oxide carriers (CA+CH+TiO2) were the most effective in H-2 production, giving a H-2 production rate of 21.3 mmol.L-1.h(-1) (at 35 degrees C and 20 g COD.L-1 of sucrose), which was over three-fold of that obtained from suspended cells (6.8 mmol.L-1.h(-1)). The sucrose conversion was essentially 85% or higher in all runs, and the biogas consisted of only H-2 and CO2. The major soluble metabolites were butyric acid, acetic acid, and propionic acid, while a small amount of ethanol was also produced. Addition of trace metal salts (Ca2+ and Ni2+) appeared to enhance the H-2 producing performance for the suspended culture, elevating H-2 production rate from 6.8 to 9.3 and 8.7 mmol.L-1.h(-1), respectively. Moreover, the immobilization matrix containing TiO2 seemed to result in better H-2 production in general.