The purpose of this study is to evaluate whether there is a difference in proportion of patients with resolution of heartburn and other symptoms related to gastroesophageal reflux disease (GERD) after four weeks of treatment with esomeprazole (NEXIUM®) in those subjects with Erosive Esophagitis (EE) and those without EE.

Inclusion Criteria:

• Symptoms of GERD as defined in this protocol: Heartburn (severity of mild, moderate or severe) 2 or more times in the 7 days prior to the Screening visit (Visit 1) and, on average, at least 2 times per week over the past 3 months.
• Male or female, 18 to 70 years old, inclusive.
• Non-pregnant, non-lactating female patients. Female patients must be postmenopausal, surgically sterile, or using a medically acceptable form of birth control, as determined by the investigator. Females of childbearing potential must agree to continue using an acceptable form of birth control throughout the conduct of the study.
• Negative urine pregnancy test for females of childbearing potential.
• Willingness to adhere to all protocol requirements.

Exclusion Criteria:

• Previous enrollment in the present study.
• Significant clinical illness within 2 weeks prior to the first dose of study medication or a significant illness during the study.
• Use of a PPI, including PRILOSEC OTC®, within 21 days of Screening (Visit 1) or at anytime during the study (Visit 1 through Visit 4).
• Daily therapy with an H2 RA within 14 days of Screening (Visit 1): eg, ranitidine (ZANTAC®), cimetidine (TAGAMET®), nizatidine (AXID®), famotidine (PEPCID®) (occasional use; ie, less than daily, is permitted).
• Use of H2 RAs at any frequency are prohibited throughout the entire study (Visit 1 through Visit 4).
• A history of gastric or esophageal surgery (including, but not limited to, Nissen fundoplication and bariatric surgery), except for simple closure of a perforated ulcer or procedures that would not affect the study as determined by the Clinical Study Team physician at AstraZeneca.
• Clinically significant gastrointestinal (GI) bleeding (eg, melena, frank hematochezia) within 3 days of Screening (Visit 1) or noted at the time of baseline EGD.
• Non-acid related etiologies of esophagitis (eg, pill-induced, caustic ingestion or eosinophilic esophagitis).

Generalized bleeding disorders resulting from hemorrhagic diathesis (such as abnormalities in clotting factors or platelets).