Planktic cyanoprokaryotes ofthe order Chroococcales are described from 192 sites in north-eastern Australia. Despite the diversity of flrehwater biotypes, and increasing evidence of seasonal cynaoprokeryote dominance in planktic habitats, particularly man-made reservoirs, this is the first detailed study documenting the cyanoprokaryote microflora from this region. Over five thousand samples were observed from which 54 Chroococcalean species were recorded representing four families. Sampling locations included natural lakes, man made reservoirs and weir pools, rivers and streams. The majority of the taxa could be regarded as cosmopolitan, followed by tropical/subtropical and temperate taxa. The most common genera recorded included Aphanocapsa, Cyanodictyon, Myxobaktron, Merismopedia and Microcystis.The highest taxon richness occurred in man-made lakes and reservoirs, followed by natural lakes, and streams and rivers. Fifty three taxa including three newly described species (Aphanocapsa annulata sp. nova, Gloeothece lacustrus sp. nova, Gloeocapsa planktonica sp. nova) are presented including information on their morphological variability, ecology and distribution.