Biological hydrogen production project is being carried out to develop renewable and environmentally acceptable energy sources. Basic research has been done to obtain capable microorganisms for hydrogen production (photosynthetic bacteria and cyanobacteria) by using genetic engineering methods. For photosynthetic bacteria, control of put promoter has been examined to regulate the expression of the photosynthetic proteins to increase the efficiency. In the case of cyanobacteria, replacement of enzyme for hydrogen production has been examined to introduce hydrogenase gene into cyanobacteria. Adding to the improvements, experiments were done to measure the light penetration precisely and its effect to hydrogen production.