With the aim of establishing suitable follow-up intervals, we examined the probability for the recurrence of relevant adenomas in the colorectum. A total of 592 adenoma patients in whom colonoscopy up to the caecum had reliably excluded relevant findings, were admitted to the study. Relevant findings were considered to be 1) colorectal carcinoma, 2) an adenoma with severe cellular atypia, 3) an adenoma of at least 5 mm in diameter, 4) a histologically unclassified polyp of at least 5 mm in diameter. We were able to show that the use of a dose-effect relationship is statistically justified for the follow-up results of the 592 patients. Thus, the probability for renewed relevant findings at any given time can be computed on the basis of the follow-up results. Renewed relevant findings were presented by 6.0% of patients with single adenomas after 4 years (confidence level 4.8-7.3%), while 5.7% of patients with multiple adenomas had relevant findings after 2 years (confidence level 4.5-7.0%). These follow-up intervals are, thanks to the adequate detection rate, economical and, at the same time, safeguard adenoma patients with a high level of reliability, against cancer of the colorectum.