Lansoprazole, a proton pump inhibitor, inactivates the H(+)/K(+)-ATPase pump in parietal cells, thereby suppressing basal and stimulated gastric acid secretion and increasing intragastric pH. After 8-12 weeks' treatment with lansoprazole, all children (n = 27) with esophagitis at baseline were healed (confirmed by endoscopy) and 76% of 62 evaluable children experienced improvements in overall gastroesophageal reflux disease (GERD) symptoms. In this noncomparative trial, 66 children (aged 1-11 years) with GERD with or without esophagitis received oral lansoprazole 15 or 30 mg once daily dependent on their weight. The drug is generally well tolerated in children with GERD. In the largest study, the most common treatment-related adverse events occurring during therapy were constipation and headache.