The purpose of the study is to evaluate the effect of esomeprazole 20 mg od versus placebo for the prevention of gastric and/or duodenal ulcers in patients taking low-dose ASA.

Inclusion Criteria:

• A clinical diagnosis of a condition (cardiovascular and/or cerebrovascular protection or other reasons) that requires daily intake of low-dose ASA, 75-325 mg, and is expected to continue for the duration of the study (daily is defined as at least 5 days per week).
• Age >= 60 years.
• No gastric and/or duodenal ulcer at the baseline endoscopy.
• H. pylori negative by serology test at screening.

Exclusion Criteria:

• Upper GI symptoms
• Erosive oesophagitis
• Malignancy