The purpose of this study is to determine the area under the plasma concentration-time curve (AUC) of esomeprazole after single oral doses of 5 mg, 10 mg or 20 mg esomeprazole in pediatric patients 1 to 11 years-old inclusive with endoscopically-proven GERD.

Inclusion Criteria:

• Patients must be able to take solid or bland food (eg, applesauce).
• Patients must weigh at least 8 kg and at the investigator's discretion be able to undergo extraction of an adequate volume of blood.
• The patient's weight for height percentile should be less than the 90th percentile and/or the BMI must be between the 5th and 85th percentile for age.
• Patients must be diagnosed with endoscopically-proven GERD

Exclusion Criteria:

• Use of any other investigational compound or participation in another clinical trial within 28 days prior to the screening visit.
• History or presence of gastrointestinal, hepatic or renal disease or other conditions that could interfere with absorption, distribution, metabolism or excretion of esomeprazole.
• Unstable diabetes mellitus or history of seizure disorder.
• Any acute or chronic illness or a medical history, which in the opinion of the investigator and/or sponsor, could compromise the patient's safety or successful participation in the study.