Hydrogen (H-2) is a renewable, abundant, and nonpolluting source of energy. Photosynthetic organisms capture sunlight very efficiently and convert it into organic molecules. Cyanobacteria produce H-2 by breaking down organic compounds and water. In this study, biological H-2 was produced from various strains of cyanobacteria. Moreover, H-2 accumulation by Synechocystis sp. PCC 6803 was as high as 0.037 umol/mg Chl/h within 120 h in the dark. The wild-type, filamentous, non-heterocystous cyanobacterium Desertifilum sp. IPPAS B-1220 was found to produce a maximum of 0.229 mu mol/mg Chl/h in the gas phase within 166 h in the light, which was on par with the maximum yield reported in the literature. DCMU at 10 mu M increased H-2 production by Desertifilum sp. IPPAS B-1220 by 1.5-fold to 0.348 mu mol H-2/mg Chl/h. This is the first report on the capability of Desertifilum cyanobacterium to produce H-2. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.