Photofermentative hydrogen production is challenged by the photobioreactor design that can overcome poor light penetration, agitation and temperature control. Flat panel reactors have been reported to have several advantages over other reactors. But they are limited to a suitable type of agitation system when using it for hydrogen production. The aim of the present study is to develop and improve a flat panel reactor that can overcome the problem of agitation with a rocking motion. Studies with Rhodobacter sphaeroides O.U. 001 resulted in a cumulative hydrogen production of 492 +/- 10 mL with maximum production rate of 11 mL L(-1) h(-1), substrate (malic acid) conversion efficiency of 44.4% and light conversion efficiency of 3.31%. The mixing time of the reactor was found to be around 17 s with a power input of 100-275 W/m(3). Though the entire reactor was in motion the energy spent for the rocking motion was found to be quite low. Copyright (C) 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.