This study evaluates PGE2 production, COX-2 enzyme activity and PCNA expression in Barrett's metaplastic tissue. All patients will have a baseline endoscopy with multiple biopsies. The patients will then be receive four dosing regimens (esomeprazole, esomeprazole and aspirin, esomeprazole and rofecoxib, or rofecoxib alone) consecutively each for a 10 day dosing period, whilst undergoing further follow up endoscopies and multiple biopsies.

Inclusion Criteria:

• A biopsy-proven diagnosis of Barrett's esophagus segment length greater than 2cm with no dysplasia or adenocarcinoma.
• Clinically normal laboratory results and physical findings at screening.

Exclusion Criteria:

• A history of esophageal, gastric or duodenal surgery, including antireflux surgery or endoscopic antireflux procedures, except for simple closure of an ulcer.
• Evidence of the following diseases or conditions:
• Barrett's esophagus less than or greater than 2cm that is positive for high grade dysplasia or adenocarcinoma
• Signs and symptoms of gastric outlet obstruction
• Active peptic ulcer disease
• severe liver disease
• Pancreatitis
• Malabsorption
• Active inflammatory bowel disease
• Severe pulmonary, cardiovascular or renal disease
• Impaired renal function or abnormal urine sediment on repeated examinations
• esophageal stricture or active, severe esophagitis.