Twenty-one participants from Europe, North America and China convened in Chongqing, China, October 12-14, 2005, for the Eighth International Symposium in Fish Physiology, Toxicology and Water Quality. The subject of the meeting was Hypoxia in vertebrates: Comparisons of terrestrial and aquatic vertebrates. These Proceedings include 13 papers presented over the three day period and discuss the responses of fish, reptiles and mammals to hypoxia. These papers report on the responses of animals to hypoxia at the behavioural, physiological and molecular levels. Clearly hypoxia has wide ranging effects, the responses are complex and there are many similarities in the responses of all vertebrates to hypoxia. Organisms respond to hypoxia by reducing energy expenditure, in particular inhibiting reproduction, feeding and exercise. That is animals only expend energy that is absolutely necessary for survival. There is extensive reorganization of cellular machinery directed by hypoxia inducible factors (HIFs), proteins that increase during hypoxia and have a marked effect on the expression of many genes. As a result, anaerobic metabolism is up regulated and many aspects of aerobic metabolism are down regulated. Many cells enter cell cycle arrest. Thus organisms stop reproducing and growing during hypoxia and if the effects of hypoxia are severe, development of eggs and larvae is compromised.