Two species of widespread Antarctic algae were investigated with molecular genetics approaches to determine if they are two separate species. Prasiola crispa usually forms a sheet like growth on moist soil near bird colonies and Prasiola calophyll usually forms ribbon like growths attached to stones in glacial meltstreams. Microscopically they appear identical and in some cases they produce ... identical macroscopic growth forms. Specimens of both species were collected from widely spaced locations. P. crispa from Cape Geology and Cape Royds and P. calophylla from Cape Geology, Taylor Valley and Cape Royds. Together with specimens collected in previous season at other localities and material sent by overseas workers, samples were used to extract DNA for comparison to help solve the taxonomic problem of species identification. Nuclear rDNA ITS sequence methodology was used.