A select set of microalgae are reported to be able to catalyse photobiological H(2) production from water. Based on the model organism Chlamydomonas reinhardtii, a method was developed for the screening of naturally occurring H(2)-producing microalgae. By purging algal cultures with N(2) in the dark and subsequent illumination, it is possible to rapidly induce photobiological H(2) evolution. Using NMR spectroscopy for metabolic profiling in C. reinhardtii, acetate, formate, and ethanol were found to be key compounds contributing to metabolic variance during the assay. This procedure can be used to test algal species existing as axenic or mixed cultures for their ability to produce H(2). Using this system, five algal isolates capable of H(2) production were identified in various aquatic systems. A phylogenetic tree was constructed using ribosomal sequence data of green unicellular algae to determine if there were taxonomic patterns of H(2) production. H(2)-producing algal species were seen to be dispersed amongst most clades, indicating an H(2)-producing capacity preceded evolution of the phylum Chlorophyta.