The pharmacology, pharmacodynamics, pharmacokinetics, clinical efficacy, and adverse effects of esomeprazole are reviewed. Esomeprazole, a proton-pump inhibitor (PPI), is the S-isomer of omeprazole. Esomeprazole has FDA-approved labeling for use in the treatment of symptomatic gastroesophageal reflux disease (GERD), including healing and maintenance of healing of erosive esophagitis and as part of a triple-drug regimen for Helicobocter pylori infection. Esomeprazole is structurally similar to other PPIs but is the first PPI to include only the active isomer, which may lead to improved pharmacokinetic and pharmacodynamic characteristics. Esomeprazole maintains intragastric pH at a higher level and above 4 for a longer period than other PPIs. Clinical studies have shown that esomeprazole is at least equivalent in safety and efficacy to other drugs in the class. Esomeprazole has demonstrated efficacy in the treatment of erosive esophagitis, the maintenance of healing of erosive esophagitis, and the treatment of signs and symptoms of GERD. Effective dosages are 20 or 40 mg orally every day or as needed. Esomeprazole magnesium 40 mg once daily in combination with amoxicillin and clarithromycin is effective in eradicating H. pylori infection. The potential for interacting with other drugs is limited and is similar to that of omeprazole. The most common adverse effects are headache, respiratory infection, and abdominal symptoms. Esomeprazole has pharmacokinetic properties that may make it more effective than omeprazole in some patients.