Inhibition of acetate addition on hydrogen production from sucrose-rich synthetic wastewater by mixed anaerobic culture was investigated in this study. Experimental results showed that the added acetate had a significant influence on both substrate degradation and hydrogen production during the fermentation process. The distribution of aqueous products was also influenced by the acetate addition. Modified logistic equations were able to simulate the acidogenesis process well, while a noncompetitive product inhibition model was successfully used to describe the inhibitory effects of acetate addition on both substrate degradation and hydrogen production. From kinetic analysis, the maximum specific rate r(max) = 584.9 mg/g VSS/h, inhibition constant K-C = 8.27 g/l and the exponent of inhibition n = 1.53 were estimated for sucrose degradation, whereas r(max) = 221.7 ml/gVSS/h, K-C = 9.44 g/l and n = 1.52 were calculated for hydrogen production. In addition, the C-I,C-50 values of added acetate on the specific hydrogen production rate and hydrogen yield were 11.05 and 31.90 g/l, respectively. The fermentation patterns in the reactor were substantially changed because of the acetate addition, especially at higher dosages. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.