The objective of conducting experiments in a laboratory is to gain data that helps in designing and operating large-scale biological processes. However, the scale-up and design of industrial-scale biohydrogen production reactors is still uncertain. In this paper, an established and proven Eulerian-Eulerian computational fluid dynamics (CFD) model was employed to perform hydrodynamics assessments of an industrial-scale continuous stirred-tank reactor (CSTR) for biohydrogen production. The merits of the laboratory-scale CSTR and industrial-scale CSTR were compared and analyzed on the basis of CFD simulation. The outcomes demonstrated that there are many parameters that need to be optimized in the industrial-scale reactor, such as the velocity field and stagnation zone. According to the results of hydrodynamics evaluation, the structure of industrial-scale CSTR was optimized and the results are positive in terms of advancing the industrialization of biohydrogen production. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.