Hydrogen (H-2) production was studied using a non-heterocystous, filamentous cyanobacterium, Lyngbya perelegans in free and immobilized forms, where cells were incubated under 02 free anaerobic environment with alternate light and dark period (21 h light/3 h dark). For immobilization, agar and alginate systems were taken and it was revealed that hydrogen production was more sustained in alginate trapped cells as compared to agar trapped cells and free cells. Cell density and size of bound cell system were also important parameters influencing H-2 production in immobilized systems. The type of gas mixtures sparged for creating anoxic environment in the headspace had a significant influence on H-2 production showing methane (CH4) to be most conducive component of the gaseous mixture. (C) 2014 Elsevier Ltd. All rights reserved.