The influences of initial pH (4.0-9.0), iron concentration (1.2-100 mgll), nitrogen concentration (NH4HCO3, 0.56-11.28 gll) and starch concentration (2-32 gll) on hydrogen production and volatile fatty acid (VFA) production were studied. Batch experiments using starch as a substrate and mixed bacteria were conducted at 35degreesC. The optimum pH. iron concentration and nitrogen concentration for hydrogen production at a starch concentration of 15 gll were 7.0-8.0, Fe2+ 10 mgll and NH4HCO3 5.64 gll, respectively. The typical VFAs were acetate, propionate and but,rate, with acetate as the major component. The maximum specific hydrogen production rate of 146 ml/g-VSS (.) d (volatile suspended solids, VSS) and the hydrogen yield of 178 ml/g-starch were. obtained at a starch concentration of 15 gll under optimum environmental conditions. The maximum hydrogen vield of 194 ml/g-starch was obtained at a starch concentration of 2 gll. The maximum specific hydrogen production rate of 237 ml/g-VSS (.) d was found at a starch concentration of 24gll.