the aim of this study was to investigate the maximum hydrogen yield as well as the chemical oxygen demand reduction from palm oil mill effluent by using two stage sequential dark and photo fermentation. The first stage operation was carried out using Clostridium butyricum LS 2, which has the maximum hydrogen yield of 0.784 ml H2/ml POME and COD removal of 57%. The dark fermentative effluent was diluted with 50%of tap water.