The effect of coculture of Clostridium butyricum and Escherichia coli on hydrogen production was investigated. C. butyricum and E. coli were grown separately and together as batch cultures. Gas production, growth, volatile fatty acid production and glucose degradation were monitored. Whilst C. butyricum alone produced 2.09 mol-H(2)/mol-glucose the coculture produced 1.65 mol-H(2)/mol-glucose. However, the coculture utilized glucose more efficiently in the batch culture, i.e., it was able to produce more H(2) (5.85 mmol H(2)) in the same cultivation setting than C. butyricum (4.62 mmol H(2)), before the growth limiting pH was reached. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.