The effect of butyrate addition on H(2) production from acetate by purple non-sulphur photosynthetic bacteria Rhodopseudomonas faecalis RLD-53 was studied in this work. Experimental results showed that butyrate was not used as carbon source for H(2) production, but different concentration (12.5-100 mmol/l) of butyrate added in acetate medium has obviously affected H(2) yield and maximum H(2) production rate. H(2) yield and maximum H(2) production rate increased with the increasing of butyrate concentration when butyrate concentrations at 12.5-25 mmol/l and then gradually decreased when the butyrate concentration by further increase to 100 mmol/l; this indicated that the increase of butyrate would lead to the inhibition of H(2) production. H(2) yield (3.43 mol-H(2)/Mol-acetate) and maximum H(2) production rate (32.54 ml/l/h) were the highest when acetate was at 25 mmol/l and butyrate at 25 mmol/l. These are higher than most reported values in the literature. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.