Dosing information, aged-specific pharmacodynamic and pharmacokinetic data are not available in infants, aged 0-12 months. Two adult studies at healthy volunteers suggest that an omeprazole suppository is an effective dosage form.This study is designed to evaluate and to compare the efficacy, the pharmacodynamics and the pharmacokinetics of oral and rectal omeprazole treatment in infants with gastroesophageal reflux disease.