Biohydrogen production from suspended, biofilm, or granular sludge fed with a glucose substrate was examined in a continuous stirred tank reactor (CSTR) and anaerobic fluidized bed reactors (AFBRs) operating at a temperature of 37 degrees C and a pH of 5.5. Comparing with a hydrogen production rate of 0.32 L/(L center dot h) by suspended sludge in the CSTR, a 10-fold and a more than 20-fold increases in hydrogen production rate were achieved by granular sludge in the CSTR and granular or biofilm sludge in AFBRs, respectively, while keeping a comparable hydrogen yield with the suspended culture. Although a comparable performance in hydrogen production was demonstrated by both granular sludge and biofilm in the AFBRs, the biofilm may be washed out and replaced completely in a longer term of operation. Formation of granular sludge and biofilm substantially enhanced biomass retention which was closely associated with reactor configuration and hydrogen production performance. A granule-base column-shaped reactor system appears to be the preferred process for continuous hydrogen fermentation on glucose substrate.