To identify genes important for the photoproduction of H(2) of Chlamydomonas reinhardtii, random insertional mutants, by the ble gene encoding the enzyme with zeomycin resistant properties, were screened for clones with changed H(2) production. One of the mutants, denoted T1, with 7.8-fold of H(2) yield and about 23% of respiration rate increased compared with the parental strain cc849 was obtained among the zeomycin-resistant transformants. The photosynthetic rate and Fv/Fm, the efficiency of PSII primary photochemistry of T1 declined. Therefore, the photosynthesis/respiration capacity ratio (P/R ratio) of T1 was reduced compared with strain cc849. However, the growth of the mutant T1 was not inhibited, indicating that T1 was a good mutant for further studies of the genes improving H(2) yield by lowering the photosynthetic capacity and/or enhancing the respiration capacity in C. reinhardtii, and had potential to be used in further improvement of H(2) generation by further biotechnological approaches. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.