This volume represents the proceedings of the 9th International Proton Transport Conference, "Mechanisms and Consequences of Proton Transport" held in Leura, Australia, August 19 -21, 200 I. This conference has been held since 1971 every 3 to 4 years with few exceptions in association with the Congress of the International Union of Physiological Sciences. The first meeting was held in Frankfurt, Germany, at the Max-Planck'Institute. Countries hosting the conference have been Germany (twice), Sweden (twice), India, Canada, USA, Great Britain, and now Australia. Over the past 30 years participants at these Proton Transport Conferences have been principal contributors to the major discoveries in the physiology, biochemistry and pharmacology of gastric acid secretion. These include development of the H2-receptor blockers, defining the signaling pathways for the regulation of acid secretion, identifying the gastric proton pump, discovery and development of proton pump inhibitory drugs, and elucidating the physiology and biochemistry of Helicobacter pylori.