This study was to compare the effect of 156 weeks of treatment with MK-0966 (Rofecoxib) versus placebo on the recurrence of colorectal adenomas (growths that occur on the inside (the lining) of the large intestine, also known as the colon) in patients with a history of colorectal adenomas.

Inclusion Criteria:

• Eligible patients must have undergone a complete colonoscopy within 12 weeks of study entry with removal of all polyps; at least one polyp must have been confirmed a large bowel pre-cancerous polyp (adenoma) by the study pathologist.

Exclusion Criteria:

• History with a specific hereditary large bowel polyp syndrome
• History of a large bowel adenoma before age 35
• Small or large bowel resection or history of inflammatory bowel disease
• History of cancer within the five years before enrollment
• Expected need for chronic NSAID therapy
• Positive test result for stool occult blood
• Uncontrolled hypertension, stroke or temporary mini stroke (TIA) within the past 2 years, angina or congestive heart failure with symptoms that occur at rest or with minimal activity
• History of myocardial infarction (heart attack), coronary angioplasty, or coronary artery bypass grafting within the past 1 year
• Pregnancy