To better understand the possible role of deoxygenation of haemoglobin in the pathogenesis of exophthalmos in the West Australian dhufish, Glaucosoma hebraicum Richardson, some oxygen transport properties of haemoglobin from this species were determined and compared with haemoglobin from black bream, Acanthopagrus butcheri (Munro), snapper, Pagrus auratus (Bloch & Schneider) and King George whiting, Sillaginodes punctata (Cuvier). Dhufish had a single haemoglobin with a pronounced Root effect. Snapper and black bream blood had six and five types of haemoglobin, respectively. The magnitude of the Root effect of haemoglobins in the haemolysate was demonstrated by comparing oxygenation and total deoxygenation at pH 8 with relative deoxygenation at pH 6.9. Dhufish haemoglobin demonstrated a large Root effect, with the Root effect of King George whiting, snapper and black bream being of lesser magnitude. Deoxygenation of all haemolysates was more pronounced in the presence of adenosine triphosphate (ATP). Seasonal changes in haematological parameters and ATP content of dhufish blood were not evident. The Root effect is discussed in the context of its possible role in oxygen supply to the retina and adaptation to the fish's habitat and the environment.