Large-scale hydrogen production by Spirulina and Anabaena spp. has been tried using different types of bioreactors that included vertical column reactor, tubular type and flat panel photobioreactor (Dutta et al. 2005). These reactors were designed to make use of solar light for illumination, to maximize the area for incident light (high surface to volume ratio) and to allow sterilization and hydrogen collection with convenience and ease. Nevertheless, the reactors are subjected to continuous modification in order to increase their productivity and to decrease costs of maintenance and production. So far, these modifications succeeded in bringing down the cost of biologically produced hydrogen to $25 per m3 compared to $170 per m3 for the hydrogen produced by splitting of water (Block and Melody 1992). Increased production of hydrogen was also achieved by genetically modifying the nitrogenase enzyme in hydrogen-producing strains. The ongoing research on hydrogen production by cyanobacteria focuses on finding new strains with higher potential to produce hydrogen, optimizing the mass production of hydrogen in bioreactors and modifying the physiology and the genetic system of H2-producing cyanobacteria to ensure maximum production of hydrogen.