Malignancy potential of colorectal polyps increases with size. The growth rate and destiny of each polyp is virtually unknown. It was recently shown that polyps smaller than 10 mm left in situ may partly regress or partly increase in size, whereas one quarter of polyps are unchanged after 3 years. Polyps smaller than 5 mm show a mean increase in size, whereas polyps measuring 5 to 9 mm show a mean decrease in size. Methodologic problems with the measurement of polyps and cancer are discussed. More studies of polyp growth related to risk factors are warranted.