Anaerobic mixed culture acclimated with sucrose was used as inoculum in batch experiments to investigate the effects of various parameters on biological hydrogen production from sucrose. In particular, the effect of the culture temperature has been investigated in detail. The optimum of the iron concentration in the external environment on hydrogen production was also studied at different temperatures. Experimental results show that the hydrogen production ability of the anaerobic bacteria was deeply affected by both culture temperature and iron concentration. Increasing the culture temperature favored the production of hydrogen when it was in the range of 25-40 degrees C, and high sucrose conversion efficiencies (ca. 98%) were consistently obtained with the mixed bacteria at the same time. While the temperature went on increasing to 45 degrees C, the hydrogen production was almost inhibited. The optimum concentrations of iron for hydrogen production decreased obviously along with increasing the reactor's temperature. For 25, 35, and 40 degrees C, the maximum production yield of hydrogen were 356.0, 371.7, and 351.1 ml obtained at the iron concentration of 800, 200, and 25 mg FeSO4 1(-1), respectively. (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All fights reserved.