Hydrogen gas production with simultaneous COD removal was realized by application of DC voltages (0.5-5.0 V) to landfill leachate. The rate and the yield of hydrogen gas production were investigated at different DC voltages by using aluminum electrodes and DC power supply. The highest cumulative hydrogen production (5000 mL), hydrogen yield (2400 mL H(2) g(-1) COD), daily hydrogen gas formation (1277 mL d(-1)), and percent hydrogen (99%) in the gas phase were obtained with 4 V DC voltage. Energy conversion efficiency (H(2) energy/electrical energy) reached the highest level (80.6%) with 1 V DC voltage. Hydrogen gas production was mainly realized by electrohydrolysis of leachate organics due to negligible H(2) gas production in water and leachate control experiments. The highest COD removal (77%) was also obtained with 4 V DC voltage. Electrohydrolysis of landfill leachate was proven to be an effective method for hydrogen gas production with simultaneous COD removal. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.