One-third of individuals over the age of 55 years have single or multiple colorectal adenomas. During a subsequent period of 10 years, 3-5% of adenoma-bearing individuals will probably develop a carcinoma. The rather low conversion rate from benign to malignant disease indicates that most individuals with adenomas will never develop colorectal carcinoma. More knowledge is required to predict the outcome of the individual adenoma in a given patient. This will probably be obtained by increasing progress within gene technology and through large prospective follow-up studies of adenoma-bearing patients.