This work investigates the exploitation of olive mill wastewater (OMW) for producing hydrogen in a membrane reformer. Olive mill wastewater was filtered and then concentrated via distillation. The intermediate distillate (about 49 wt%) with 10,600 mg L-1 total organic carbon (TOC) was used to feed a membrane reactor consisting of a dense Pd-Ag permeator tube filled with Pt-based catalyst. The reforming tests were conducted at 450 degrees C in the pressure range 100-500 kPa by varying the space velocity from 2.78 x 10(-3) to 8.33 x 10(-3) mol h(-1) g(cat)(-1). The Pd-Ag tube selectively separated the produced hydrogen, while the retentate stream-mainly containing non-permeated hydrogen, CO2 and methane-was collected from the shell side. Gas chromatographic analysis verified the presence of side reactions (hydrogenolysis, cracking, etc.) and the deactivation of the catalyst due to the carbon formation. The hydrogen recovery was positively affected by the pressure; its highest values (over 90%) were attained at 500 kPa, while the maximum hydrogen yield was measured at 300 kPa with a space velocity of 5.56 x 10(-3) mol h(-1) g(cat)(-1). Up to 2 kg of permeated hydrogen was produced per ton of olive mill wastewater. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.