Previous studies of the genus Atherinomorus suggested that A. lacunosus was one species with a very wide range over the Indian and Pacific Oceans. Morphology (including osteology) and meristics of many populations of Atherinomorus were studied to test this hypothesis. The results indicate that there are two species pairs of Atherinomorus around the coast of Australia. Each of the four species can be distinguished by the combination of meristic and morphological characters. This study was supplemented with an electrophoretic analysis on a limited collection of fish from the western, northern and eastern coasts of Australia.