Esomeprazole (Nexium); S-omeprazole) is a single optical isomer proton-pump inhibitor (PPI) approved for the management of reflux oesophagitis, the symptomatic treatment of gastro-oesophageal reflux disease (GORD), the prevention and healing of NSAID-associated gastric ulcer disease (and the prevention of NSAID-associated duodenal ulcers in the UK), the treatment of Helicobacter pylori infection and associated duodenal ulcer disease (and prevention of relapse of H. pylori-associated peptic ulcers in the UK), and the treatment of Zollinger-Ellison syndrome (and other hypersecretory syndromes in the US).Once-daily oral esomeprazole 40 mg demonstrates greater antisecretory activity than other PPIs. Overall, in well designed clinical studies of 4 weeks' to 6 months' duration in patients with GORD, esomeprazole had similar or better efficacy than other agents. In patients requiring ongoing treatment with NSAIDs, co-therapy with once-daily esomeprazole 20 or 40 mg achieved relief of gastrointestinal symptoms or prevented ulcer occurrence, more effectively than placebo. Esomeprazole was also better than ranitidine 150 mg twice daily in healing NSAID-associated gastric ulcers. In addition, the drug has demonstrated efficacy as part of a triple-therapy regimen for the eradication of H. pylori infection, the healing of H. pylori associated duodenal ulcers and the prevention of relapse of gastric ulcers. Esomeprazole also effectively treated patients with Zollinger-Ellison syndrome. Esomeprazole is generally well tolerated with an adverse-event profile similar to that of other PPIs. Thus, the efficacy and tolerability of esomeprazole for the management of GORD and H. pylori eradication remains undisputed, and the data support its use for the first-line treatment of NSAID-associated gastric ulcer disease and Zollinger-Ellison syndrome.