Experiments were conducted to select a natural mixed microflora seed source and investigate the effect of temperature and pH on fermentative hydrogen (H-2) production from cattle wastewater by sewage sludge. Sewage sludge was shown to have higher cumulative H-2 production than other inoculum collected from cow dung compost, chicken manure compost, and river sludge. Experimental results show that H, production from cattle wastewater was significantly affected by both pH and temperature of the culture. The maximum H-2 yield was obtained at pH 5.5. H-2 yield and the ratio of butyrate/acetate (Bu/Ac) followed a similar production trend, suggesting that butyrate formation might favor H-2 production. The optimal temperature for H, production from cattle wastewater was 45 degrees C with peak values of H, production (368 ml), hydrogen yield of 319 ml H-2/g chemical oxygen demand (COD) consumed, and butyrate/acetate ratio of 1.43. Presence of ethanol and propionic acid indicated decreased hydrogen production; their concentrations were also affected by pH and temperature. A modified Gompertz model adequately described H-2 production and bacterial growth.