Hydrogen is a natural by-product of several microbial driven biochemical reactions, mainly in anaerobic fermentation processes. In addition, certain microorganisms produce enzymes by which H(2) from water may be obtained if an outside energy source, like sunlight, is provided. Biophotolysis is a biological process which involves solar energy and algae clusters to convert water into hydrogen. Algae pigments absorb solar energy and enzymes in the cell act as catalysts to split water into hydrogen and oxygen. There are many research activities studying hydrogen production from biological systems cyanobacteria and green algae and some studies present a complete outline of the main available pathways to improve the photosynthetic H(2) production [1,2]. Efficiency (energy produced from hydrogen divided by solar energy) of such processes can be estimated up to 10%. This value has to be increased for a large-scale hydrogen production. The effect of different artificial illumination conditions on H(2) production was studied for green algae cultures (Chlamydomonas reinhardtii). Results will be used to design a high-efficiency photobioreactor for a large-scale hydrogen production. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.